Polymerization photoinhibitor

ABSTRACT

Provided herein is technology relating to polymerization and producing polymers and particularly, but not exclusively, to methods, systems, and compositions for producing articles using three-dimensional printing and for improving control of polymerization using a polymerization photoinhibitor having fast back reaction kinetics such as hexaarylbiimidazole compounds and bridged hexaarylbiimidazole compounds.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 371 U.S. National Phase Entry of pendingInternational Application No. PCT/US2019/018511, filed Feb. 19, 2019,which claims priority to U.S. Provisional Application No. 62/632,903,filed Feb. 20, 2018; U.S. Provisional Application No. 62/632,834, filedFeb. 20, 2018; and U.S. Provisional Application No. 62/632,927, filedFeb. 20, 2018, each of which is incorporated herein by reference in itsentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under DE023771 awardedby the National Institutes of Health. The government has certain rightsin the invention.

FIELD

Provided herein is technology relating to polymerization and producingpolymers and particularly, but not exclusively, to methods, systems, andcompositions for producing articles using three-dimensional printing andfor improving control of polymerization using a polymerizationphotoinhibitor having fast back reaction kinetics such ashexaarylbiimidazole compounds and bridged hexaarylbiimidazole compounds.

BACKGROUND

Photolithographic rapid prototyping (e.g., stereolithography)technologies typically achieve reaction confinement in depth usingpatterned irradiation of a photopolymerizable resin at a wavelengthwhere the resin strongly absorbs so that a thin layer of material issolidified. Consequently, three-dimensional objects are fabricated byprogressive, two-dimensional addition of material. However, these extanttechnologies are limited by having a slow fabrication rate and requirestructures to support overhanging features.

In some polymerization strategies, a monomeric resin is polymerized byirradiating a mixture of the monomeric resin and a photoinitiator at awavelength where the photoinitiator absorbs. Activating thephotoinitator produces an activating species (e.g., a radical) thatcauses the monomer to polymerize in the region comprising the activatingspecies. Some technologies provide additional control overpolymerization by using both a photoinitiator and a photoinhibitor todefine regions of polymerization and inhibition of polymerization. Inparticular, strategies have been developed in which concurrentphotoinitiation and photoinhibition using two wavelengths of lightprovides improved control of polymerization. Accordingly, controllingpolymerization depends not only on the pattern and intensity of theirradiating wavelengths, but also on the kinetics of photoactivation andsubsequent inactivation of the photoinitiator and photoinhibitor (e.g.,by a reverse back reaction that reforms the inactivated photoinitiatorand photoinhibitor). Polymerization technologies (e.g., in particular,polymerization confinement technologies) would thus benefit fromimproved photoinhibitors and polymerization strategies involvingphotoinhibitors.

SUMMARY

The technology provided herein relates to facile, three-dimensionalphotopolymerization patterning in bulk resin. In particular, embodimentsof the technology provided herein relate to the fabrication ofthree-dimensional objects at rates unattainable by conventional rapidprototyping approaches. Further, embodiments of the technology obviatethe need for structures to support overhanging features because thesolidified material is buoyed within the monomeric liquid.

Several photoinhibitors of radical-mediated polymerizations have beendescribed, including tetraethylthiuram disulfide (“TED”; see, e.g.,Scott et al. (2009) “Two-color single-photon photoinitiation andphotoinhibition for subdiffraction photolithography” Science 324(5929):913-7, incorporated herein by reference);bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (see, e.g., U.S. Pat.No. 8,697,346, incorporated herein by reference); arylmethyl sulfones(see, e.g., Karatekin (2001) “Photocopying Living Chains. 1.Steady-State” Macromolecules 34(23): 8187-8201; and Karatekin (2001)“Photocopying Living Chains. 2. Time-Dependent Measurements”Macromolecules 4 (23): 8202-15, each of which is incorporated herein byreference); and alkyl nitrites (e.g., butyl nitrite; see Sadykov et al.“ESR study of the polymerization of methyl methacrylate photoinhibitedby butyl nitrite” Polymer Science USSR 1988, 30 (9), 2045-2049 (1988),incorporated herein by reference). See, e.g., FIGS. 1, 2, and 3.

However, identifying appropriate photoinhibitors has been challenging.For example, it has been known in the art that “a photo-cleavableterminator that does not initiate polymerization is not easilyidentified as the formation of a highly stabilized radical is required”(see, e.g., Junkers et al. (2008) “Laser Induced Marking of PolymerChains with Radical Spin Traps” Macromolecular Rapid Communications 29(6): 503-10). Moreover, previous examination of TED (FIG. 1) andbis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (FIG. 2) asphotoinhibitors of radical-mediated photopolymerization revealed severallimitations. In particular, the non-photoactivated forms of TED andrelated compounds (e.g., TEMPDS) have chain transfer activities thatretard radical-mediated polymerizations. In addition, the photoactivatedforms of TED and related compounds (e.g., TEMPDS) exhibit a low butsignificant polymerization initiation activity. Also, arylmethylsulfones (FIG. 3) produce sulfur dioxide gas during radical formation.These gas bubbles therefore form in the polymerized material, thuscompromising structural integrity and introducing artefacts. And,bubbles in the composition refract the initiating and/or inhibitingwavelengths of light and thus can affect the intended polymerizationconfinement, which produces unwanted solidification of resin outside theintended region.

Accordingly, in some embodiments the technology provided herein relatesto photoinhibitors that are activated by light to form a polymerizationinhibiting species and that have a fast back reaction that reforms theinactive photoinhibitor from the polymerization inhibiting species. Insome embodiments, when not activated by light (e.g., in the inactivestate), the photoinhibitors do not inhibit and/or do not retardpolymerization and do not have initiating activity; when activated bylight, the photoinhibitors form an inhibiting species that inhibitspolymerization and that does not initiate polymerization. Accordingly,the technology provided herein relates to photoinhibition that isquickly turned “on” and quickly turned “off” by the presence and absenceof light and that does not have undesirable inhibition and/or initiationactivities.

Consequently, production and persistence of the polymerizationinhibiting species (e.g., a radical that inhibits polymerization) occursonly where the appropriate activating wavelength irradiates thephotoinhibitor. Activated photoinhibitor that diffuses out of theirradiated region subsequently reforms the inactive state quickly (e.g.,nearly instantaneously). In some embodiments, the light-activatedphotoinhibitor compounds form polymerization inhibiting species (e.g.,polymerization inhibiting radicals) having a half-life of approximately100 ns to 100 μs to 100 ms to 100 s (e.g., 10, 20, 30, 40, 50, 60, 70,80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ns; 10, 20,30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900,or 1000 μs; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500,600, 700, 800, 900, or 1000 ms; or 0, 20, 30, 40, 50, 60, 70, 80, 90,100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 s).

In some embodiments, the technology relates to the use of aphotoinhibitor having fast back reaction kinetics that reforms theinactive photoinhibitor from the inhibiting species. In someembodiments, the photoinhibitor is activated by light in a photolysisreaction to form one or more inhibiting species (e.g., polymerizationinhibiting radicals) having a half-life of approximately 100 ns to 100μs to 100 ms (e.g., 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300,400, 500, 600, 700, 800, 900, or 1000 ns; 10, 20, 30, 40, 50, 60, 70,80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 μs; or 10,20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800,900, or 1000 ms).

In some embodiments, the photoinhibitor is activated by light in aphotolysis reaction to form one inhibiting species (e.g., apolymerization inhibiting radical) and reformation of the inactive formis not limited by diffusion and/or is not a thermally driven reaction.In some embodiments, the polymerization inhibiting radical has ahalf-life of approximately 100 ns to 100 μs to 100 ms (e.g., 10, 20, 30,40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or1000 ns; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500,600, 700, 800, 900, or 1000 μs; or 10, 20, 30, 40, 50, 60, 70, 80, 90,100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ms).

One example of a photoinhibitor that forms a polymerization inhibitingspecies that reforms the inactive compound with a fast back reaction ishexaarylbiimidazole and compounds related thereto (e.g., bridged HABIcompounds as discussed herein). Hexaarylbiimidazole (HABI) compounds(see, e.g., FIGS. 4A, 4B, 5A, 5B, 5C, 5D, 5E, and 6) address some of theproblems associated with other known photoinhibitors. While HABIs havebeen known in the art since 1960 (see, e.g., Hayashi and Maeda, Bull.Chem. Soc. Japan 33: 565) as thermochromic, photochromic, andpiezochromic compounds, they have been understood in the polymer art aspolymerization photoinitiators. See, e.g., Ahn et al. (2015)“Hexaarylbiimidazoles as Visible Light Thiol-Ene Photoinitiators” DentMater. 31(9): 1075-89, incorporated herein by reference). For example,HABI compounds were sold as photoinitiators by DUPONT under the nameDYLUX. See, e.g., Dessauer (2005) “The Invention of DYLUX Instant-AccessImaging Materials and the Development of HABI Chemistry—A PersonalHistory” Advances in Photochemistry, Volume 28: 129-261, incorporatedherein by reference in its entirety). The use of HABI compounds asphotoinhibitors was not known or predictable in the art.

When activated by the appropriate wavelength, HABI compounds undergohomolytic cleavage to form imidazolyl (e.g., lophyl) radicals. See,e.g., FIGS. 4B and 6. As produced from some HABI compounds, lophylradicals are unreactive with oxygen and have slow recombination ratesattributable to steric hindrance and electron delocalization. While thelophyl radical is very stable, the lophyl radical alone does notinitiate polymerization. Indeed, HABI photoinitiators exhibit noinitiation activity of polymerizable monomers (e.g., in particular(meth)acrylate formulations) without the presence of a hydrogen-donatingcoinitiator. Thus, when HABI compounds are used as photoinitiators ofpolymerization, HABI compounds are used with coinitiator compounds tophotoinitiate photopolymerization reactions. For example, somepolymerization systems comprise use of a coinitiator comprising a thiol.Upon production of the lophyl radical from a HABI compound, the lophylradical extracts a hydrogen from the thiol to produce a radical sulfurspecies (e.g., a sulfur comprising an unpaired electron). The radicalsulfur species initiates polymerization of the monomers in the resin.

In contrast, the present technology relates in some embodiments to theuse of HABIs as photoinhibitors of photopolymerization. In particular,HABIs exhibit several favorable attributes as photoinhibitors. As notedabove, HABI compounds do not exhibit photoinitiation activity whenirradiated. Moreover, HABI compounds do not participate in chaintransfer reactions and thus polymerization rates are not inherentlyretarded by the presence of HABI compounds. Finally, HABI compoundstypically exhibit very weak absorbance in the blue region of theelectromagnetic spectrum and moderately absorb in the near-UV region ofthe electromagnetic spectrum, thus complementing the absorbance spectrumof several photoinitiators activated by blue light. In particular,camphorquinone (CQ) is a photoinitiator commonly employed for visiblelight photopolymerization—CQ absorbs blue light with an absorption peakcentered at approximately 470 nm and absorbs poorly in the near-UV. Thecomplementary absorption spectra of HABI compounds and CQ thus provide aselective generation of lophyl or initiating radicals by irradiating acomposition comprising HABI and CQ with either near UV light or bluelight, respectively. See, e.g., FIG. 7.

The recombination rates of some HABI-derived lophyl radicals aretypically very slow, proceeding over the course of tens of seconds tominutes in solution. This slow recombination rate limits the concurrentphotoinitiation/photoinhibition exposure rate for some HABI compounds,e.g., for a patterned solidification of monomer resin formulations.

Accordingly, in some embodiments the technology comprises use of aphotoinhibitor compound having fast back reaction kinetics (e.g., HABIcompounds (e.g., HABI compounds that comprise bridged imidazole dimers.See, e.g., FIGS. 5A, 5B, 5C, 5D, and 5E)). While the recombination ofthe conventional HABI compounds is a second order reaction, therecombination of the bridged compounds proceeds as a first orderreaction. Thus, while the lophyl radicals formed from conventional HABIcompounds have a half-life of tens of seconds to several (e.g., 5 to 10or more) minutes (see, e.g., Sathe, et al. (2015) “Re-examining thePhotomediated Dissociation and Recombination Kinetics ofHexaarylbiimidazoles” Ind. Eng. Chem. Res. 54 (16): 4203-12,incorporated herein by reference), the radicals produced from thetethered HABI compounds have a half-life faster than 10 seconds, e.g.,approximately 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 second(s) to tens orhundreds of milliseconds to tens or hundreds of microseconds (e.g., lessthan 10.0, 9.9, 9.8, 9.7, 9.6, 9.5, 9.4, 9.3, 9.2, 9.1, 9.0, 8.9, 8.8,8.7, 8.6, 8.5, 8.4, 8.3, 8.2, 8.1, 8.0, 7.9, 7.8, 7.7, 7.6, 7.5, 7.4,7.3, 7.2, 7.1, 7.0, 6.9, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0,5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 4.9, 4.8, 4.7, 4.6,4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2,3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8,1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4,0.3, 0.2, or 0.1 seconds; less than 1000, 990, 980, 970, 960, 950, 940,930, 920, 910, 900, 890, 880, 870, 860, 850, 840, 830, 820, 810, 800,790, 780, 770, 760, 750, 740, 730, 720, 710, 700, 690, 680, 670, 660,650, 640, 630, 620, 610, 600, 590, 580, 570, 560, 550, 540, 530, 520,510, 500, 490, 480, 470, 460, 450, 440, 430, 420, 410, 400, 390, 380,370, 360, 350, 340, 330, 320, 310, 300, 290, 280, 270, 260, 250, 240,230, 220, 210, 200, 190, 180, 170, 160, 150, 140, 130, 120, 110, 100,90, 80, 70, 60, 50, 40, 30, 20, or 10 milliseconds; less than 1000, 990,980, 970, 960, 950, 940, 930, 920, 910, 900, 890, 880, 870, 860, 850,840, 830, 820, 810, 800, 790, 780, 770, 760, 750, 740, 730, 720, 710,700, 690, 680, 670, 660, 650, 640, 630, 620, 610, 600, 590, 580, 570,560, 550, 540, 530, 520, 510, 500, 490, 480, 470, 460, 450, 440, 430,420, 410, 400, 390, 380, 370, 360, 350, 340, 330, 320, 310, 300, 290,280, 270, 260, 250, 240, 230, 220, 210, 200, 190, 180, 170, 160, 150,140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10microseconds).

The faster recombination rates of HABIs (e.g., bridged HABIs) providefor a higher rate of patterned photoinhibition irradiation exposures andthus finds use in rapid resin solidification, e.g., in two and/or threedimensions. Thus, the technology provided herein also relates to the useof “bridged” or “tethered” photoinhibitors, such as “bridged” or“tethered” HABI compounds (see, e.g., FIGS. 5A, 5B, 5C, 5D, and 5E),that have reassociation kinetics that are faster than the reassociationkinetics of some unbridged HABI compounds.

Accordingly, embodiments of the technology provide a compositioncomprising a photoinhibitor compound having fast back reaction kinetics(e.g., a HABI photoinhibitor (e.g., a bridged HABI photoinhibitor)). Forexample, some embodiments provide a composition comprising apolymerizable monomer, a photoinitiator, and photoinhibitor compoundhaving fast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor)). In some embodiments, the compositionsfurther comprise a coinitiator.

The technology is not limited in the polymerizable monomer. Severalpolymerizable monomers are described herein. In some particularembodiments, the polymerizable monomer comprises an acrylate or amethacrylate.

The technology is not limited in the photoinitiator. Severalphotoinitiators are described herein. In some particular embodiments,the photoinitiator comprises camphorquinone.

In some embodiments, the compositions further comprise aphoton-absorbing dye.

The technology relates to the production of a polymer, e.g., athree-dimensional article made from a polymer. Accordingly, in someembodiments, the compositions further comprise a polymer produced frompolymerization of said polymerizable monomer.

In some embodiments, the photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)) forms radicals (e.g., imidazolyl radicals (e.g.,covalently linked imidazolyl radicals)) upon irradiation with anappropriate wavelength and/or intensity of light. Accordingly,embodiments relate to compositions further comprising radicals (e.g.,imidazolyl radicals (e.g., covalently linked imidazolyl radicals))formed from the photoinhibitor compound having fast back reactionkinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)). The radicals exist transiently for the duration ofirradiation with an appropriate wavelength and/or intensity of light.

The components of the compositions can be provided in various amounts,concentrations, ratios, etc. For example, in some embodiments thecomposition comprises the polymerizable monomer at a concentration of,e.g., approximately 1 to 99.99 wt % (e.g., approximately 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80,85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.1, 99.2. 99.3, 99.4,99.5, 99.6, 99.7, 99.8, 99.9, 99.95, to 99.99 wt %)). In someembodiments, the composition comprises the photoinitiator at aconcentration of 0.5 to 5 wt %. In some embodiments, the compositioncomprises the photoinitiator at a concentration of approximately 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13,0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25,0.26, 0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65,0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0,4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %). And, in someembodiments the composition comprises a photoinhibitor compound havingfast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor)) at a concentration of 1 to 5 wt %. In someembodiments the composition comprises a photoinhibitor compound havingfast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor)) at a concentration of approximately 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13,0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25,0.26, 0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65,0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0,4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %).

As described herein, the technology relates in some embodiments tovarious bridged HABI photoinhibitors. In some embodiments, the bridgedHABI photoinitiator comprises a bond linking the imidazolyl moieties. Insome embodiments, the bridged HABI photoinhibitor comprises an R grouplinking the imidazolyl moieties. For example, in some embodiments thebridged HABI photoinhibitor comprises a naphthalene-bridged HABI; insome embodiments, the bridged HABI photoinhibitor comprises a[2.2]paracyclophane-bridged HABI; and, in some embodiments the bridgedHABI photoinhibitor comprises a 1,1′-bi-naphthol-bridged HABI.

While description of HABI compounds and bridged HABI compounds isprovided herein, the technology encompasses other compounds having fastback reaction kinetics, e.g., photoactivated inhibitors that producelinked, tethered, and/or bridged moieties that inhibit polymerization ofpolymerizable monomers and that reform the inactive photoinhibitor withfast back reaction kinetics (e.g., the polymerization inhibiting radicalhas a half-life of approximately 100 ns to 100 μs to 100 ms (e.g., 10,20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800,900, or 1000 ns; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400,500, 600, 700, 800, 900, or 1000 μs; or 10, 20, 30, 40, 50, 60, 70, 80,90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ms)). In someembodiments, the moieties that inhibit polymerization of polymerizablemonomers are not linked, tethered, and/or bridged but nonetheless reformthe inactive photoinhibitor with fast back reaction kinetics.

Additional embodiments relate to a system for polymerizing a monomer toproduce a polymer. For example, some embodiments relate to producing anarticle comprising a polymer. In some embodiments, systems comprise acomposition comprising a polymerizable monomer, a photoinitiator, and aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)); a first lightsource to provide a first wavelength of light; and a second light sourceto provide a second wavelength of light. In some embodiments, the firstlight source provides patterned light. In some embodiments, the secondlight source provides patterned light. In some embodiments, the firstand/or second light sources comprises a digital light processor, liquidcrystal display, light emitting diode, digital micromirror device, ormirror array. In some embodiments, the first and/or second light sourcescomprise(s) a collimated beam or a planar waveguide. In someembodiments, the system further comprises a microcontroller configuredto control the first and/or second light sources. And, in someembodiments, the system further comprises a software object comprisinginstructions for forming a three-dimensional object.

Additional embodiments relate to methods for polymerizing apolymerizable monomer. In some embodiments, methods comprise steps of,e.g., providing a composition comprising a polymerizable monomer, aphotoinitiator, and a photoinhibitor compound having fast back reactionkinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)); irradiating said composition with a first wavelengthof light; and irradiating said composition with a second wavelength oflight. In some embodiments, the first wavelength of light is blue light.In some embodiments, the second wavelength of light is UV light. In someembodiments, methods comprise irradiating with a pattern of said firstwavelength. In some embodiments, methods comprise irradiating with apattern of said second wavelength. Further, in some embodiments, themethods comprise varying the intensity of the first and/or secondwavelength of light. In some embodiments, the methods comprise moving asource of the first wavelength of light and/or moving a source of thesecond wavelength of light. In related method embodiments, methodscomprise providing a composition comprising a polymerizable monomer, aphotoinitiator, and a photoinhibitor compound having fast back reactionkinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)); producing a photoinitiation region in said compositionwith a first wavelength of light; and producing a photoinhibition regionin said composition with a second wavelength of light.

In some embodiments, the technology comprises use of a photoinitiatorand a photoinhibitor having complementary absorption spectra. In someembodiments, the photoinhibitor has fast back reaction kinetics. In someembodiments, the photoinhibitor is a hexaarylbiimidazole (HABI)compound. In some embodiments, the photoinhibitor is a bridgedhexaarylbiimidazole (HABI) compound (e.g., a bridged HABI compoundhaving a kinetically fast back reaction that reforms the HABI from thephotolytic radical products of the forward reaction). In someembodiments, the photoinitiator and photoinhibitor are provided in acomposition comprising a photopolymerizable resin formulation and thecomposition is irradiated with two overlapping irradiation patterns atwavelengths that independently effect either polymerization initiationor inhibition. The overlapping irradiation patterns produce a definedregion of polymerization that is confined in depth within a volume ofthe resin. Whereas the polymerization initiating species are generatedby irradiation at one wavelength effect rapid, irreversiblesolidification of the liquid resin in regions exclusively under exposureby that wavelength, the polymerization inhibiting species transientlygenerated by irradiation at the second, independent wavelengthsufficiently reduce the polymerization rate to prevent solidification ofthe resin in volumes concurrently exposed to both wavelengths orexclusively to the second wavelength. As the resin solidification isirreversible and the polymerization inhibiting species recombine in thedark (e.g., nearly instantaneously), the technology provides for thefabrication of arbitrary three-dimensional objects using a series ofpatterned irradiation exposures.

The technology provides several advantages over extant, conventionaltechnologies. For instance, processing is much faster than conventionalstereolithography or competing rapid prototyping technologies and thesolidified object is near-neutrally buoyant in the liquid resin,eliminating the need for overhang support structures. In addition, awide range of polymerizable monomers can be used with the technologydescribed herein relative to conventional technologies because the resinis stationary during object solidification. In particular, in someembodiments, the technology comprises use of viscous monomers or highlyfilled materials (e.g., if the filler is transparent and index-matchedto the resin) that are incompatible with conventional three-dimensionalprinting methods.

Accordingly, provided herein is a method of producing a polymerizedarticle. In particular embodiments, the method comprises providing acomposition comprising a polymerizable monomer, a photoinitiator, and aphotoinhibitor (e.g., a photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor))); irradiating said composition with a first wavelengthof light; and irradiating said composition with a second wavelength oflight. In some embodiments, the first wavelength of light is blue light.In some embodiments, the second wavelength of light is UV light.Furthermore, in some embodiments, irradiating with the first wavelengthcomprises irradiating with a pattern of said first wavelength. And, insome embodiments, irradiating with the second wavelength comprisesirradiating with a pattern of said second wavelength. As describedherein, in some embodiments, the volume of the composition irradiated bysaid first wavelength of light and the volume of the compositionirradiated by said second wavelength of light overlap at leastpartially. In some embodiments, the angle between the irradiation by thefirst wavelength of light and the irradiation by the second wavelengthof light is approximately 90°. In some embodiments, the first and secondwavelengths of light irradiate the composition from approximately thesame direction (e.g., at an angle of approximately 0°). The technologyis not, however, limited to these angles and various embodimentscomprise the first and second wavelengths irradiating the composition atany angle from 0 to 180° as described herein (e.g., 0, 5, 10, 15, 20,25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105,110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, or180°).

In some embodiments, the first and/or second wavelengths of lightirradiate the composition from multiple sources and from multipledirections. That is, in some embodiments, a plurality of sources (e.g.,a first source of the first wavelength, a second source of the firstwavelength, etc.) irradiates the composition with the first wavelengthfrom more than one direction. The technology is not limited in theangles between the plurality of sources that irradiates the compositionwith the first wavelength and thus various embodiments compriseproviding angles between any two sources providing the first wavelengthto be any angle from 0 to 180° as described herein (e.g., 0, 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100,105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170,175, or 180°). In some embodiments, a plurality of sources (e.g., afirst source of the second wavelength, a second source of the secondwavelength, etc.) irradiates the composition with the second wavelengthfrom more than one direction. The technology is not limited in theangles between the plurality of sources that irradiates the compositionwith the second wavelength and thus various embodiments compriseproviding angles between any two sources providing the first wavelengthto be any angle from 0 to 180° as described herein (e.g., 0, 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100,105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170,175, or 180°).

Embodiments relate to providing light that varies in wavelength, shape,intensity, and/or pattern. Thus, in some embodiments, methods compriseirradiating with a time-varying pattern of a first wavelength. And, insome embodiments, methods comprise irradiating with a time-varyingpattern of a second wavelength. In some embodiments, the first and/orsaid second wavelength is provided by a digital light processor, liquidcrystal display, light emitting diode, digital micromirror device, ormirror array. In yet further embodiments, methods comprise providing areaction vessel, e.g., to hold a composition as described herein.

Further embodiments are related to systems for producing an articlecomprising polymer. In particular, in some embodiments, a systemcomprises a composition comprising a polymerizable monomer, aphotoinitiator, and a photoinhibitor (e.g., a photoinhibitor compoundhaving fast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor))); a first light source to provide a firstwavelength of light; and a second light source to provide a secondwavelength of light. In some embodiments, the first light sourceprovides patterned light. In some embodiments, the second light sourceprovides patterned light. In some embodiments, the first light sourceirradiates said composition at approximately 90° relative to the secondlight source. In some embodiments, the first light source irradiatessaid composition from the same direction as the second light source(e.g., at an angle of approximately 0°). The technology is not, however,limited to these angles and various embodiments comprise the first andsecond sources irradiating the composition with the first and secondwavelengths of light at any angle from 0 to 180° as described herein.

In some embodiments, the system comprises a digital light processor,liquid crystal display, light emitting diode, digital micromirrordevice, or mirror array. For example, in some embodiments, the firstand/or second light sources comprises a digital light processor, liquidcrystal display, light emitting diode, digital micromirror device, ormirror array. In some embodiments, the first and/or second light sourcescomprises a collimated beam or a planar waveguide. In some embodiments,a first and/or second source is controlled by a computer ormicrocontroller. Accordingly, in some embodiments, systems furthercomprise a microcontroller configured to control the first and/or secondlight sources. In some embodiments, systems further comprise a softwareobject comprising instructions for forming a three-dimensional object.In some embodiments, systems further comprise a reaction vessel. In someembodiments, systems further comprise a pattern generator, mask, orother component to produce patterned light (e.g., from the first and/orsecond sources). In some embodiments, the first and/or second lightsource provides a time-varying intensity or pattern of the first and/orsecond light source. In some embodiments, a computer provides control toprovide said time-varying intensity or pattern of the first and/orsecond light source.

The technology finds wide use. For example, embodiments are related touse of a polymerizable monomer, a photoinitiator, a photoinhibitor(e.g., a photoinhibitor compound having fast back reaction kinetics(e.g., a HABI photoinhibitor (e.g., a bridged HABI photoinhibitor))), afirst wavelength of light, and a second wavelength of light to produce athree-dimensional object. For example, in some embodiments thetechnology relates to use of a photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)) for three-dimensional printing, stereolithography, orcontinuous liquid interface printing (CLIP). In some embodiments, thetechnology relates to use of a photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)) to produce a three-dimensional object.

In some embodiments, the technology finds use for improved productionand control of dead zones for continuous printing (e.g.,three-dimensional printing). In particular, embodiments of thetechnology provide compositions, methods, kits, and systems to produce adead zone during a continuous printing process using two wavelengths oflight—a first wavelength of light inhibits polymerization in a localizedregion at the projection window and a second wavelength of lightinitiates polymerization (e.g., deeper into the resin composition). Thetechnology provides facile control over the dead zone thickness at awide range of polymerizing light intensities and provides for theproduction of larger dead zones. Accordingly, the technology increasesthe speed of continuous printing and especially improves the speed ofprinting large cross sectional area items.

Accordingly, provided herein is technology related to a method ofproducing a polymerized item. For example in some embodiments, themethod comprises providing a composition comprising a polymerizablemonomer, a photoinhibitor, and a photoinitiator; irradiating saidcomposition with a first wavelength of light to produce a dead zonecomprising an inhibiting species produced from the photoinhibitor; andirradiating said composition with a second wavelength of light toproduce an initiating species from the photoinitiator above the deadzone, wherein said initiating species polymerizes polymerizable monomersto produce at least a portion of said polymerized item. The technologyprovides a dead zone having a thickness larger than is provided byextant technologies, e.g., technologies dependent on a dead zoneproduced by O₂ replenished to the dead zone by diffusion. For example,in some embodiments, the technology provided herein relates to producinga dead zone having a thickness of at least 0.5 mm (e.g., at least 0.5,0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or2.0 mm or more). In particular embodiments, the dead zone has athickness of at least 1 mm. In some embodiments, methods furthercomprising providing a reaction vessel comprising an opticallytransparent window. And, in some embodiments of methods, the intensityof the first wavelength and the intensity of the second wavelength oflight provide that the second wavelength of light activates thephotoinitiator deeper into the composition than the first wavelength oflight activates the photoinhibitor. Methods provide a CLIP-liketechnology for producing items from a polymer. Accordingly, in someembodiments, methods further comprise providing a build plate to supportand/or move the polymerized item (e.g., vertically up out of thecomposition). Some embodiments comprise moving vertically the item or atleast a portion of said polymerized item.

In some embodiments, the second wavelength of light is provided as apatterned light, e.g., in some embodiments the second wavelength oflight is provided as a time-varying patterned light. In someembodiments, the second wavelength of light is provided by a pluralityof pixels and the intensity of each pixel is independently controlled.In some embodiments, the methods further comprise changing the patternof said second wavelength of light.

The technology produces items having a cross-sectional area, or itemscomprising portions having a cross-sectional area, that is/are largerthan the cross-sectional areas produced by extant technologies. Forinstance, in some embodiments, the polymerized item or portion thereofhas a cross sectional area of more than 1 cm², e.g., in someembodiments, the polymerized item or portion thereof has a crosssectional area of 1 to 10 cm² (e.g., more than 1, 1.5, 2, 2.5, 3, 3.5,4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or more than 10cm²).

In some embodiments, the composition does not comprise O₂. And, in someembodiments, the composition does not comprise an inhibitingconcentration of O₂. In some embodiments, the composition comprises alight absorbing component, e.g., to attenuate the intensity of the firstand/or second wavelengths of light.

Related embodiments are related to a system for producing an item from apolymerizable monomer. For example, in some embodiments systems comprisea reaction vessel comprising an optically transparent window; acomposition comprising a polymerizable monomer, a photoinhibitor, and aphotoinitiator; a first light source providing a first wavelength oflight; a second light source providing a second wavelength of light; anda vertically movable build plate. In some embodiments, the reactionvessel holds said composition. In some embodiments, the first wavelengthof light and said second wavelength of light irradiate said compositionthrough said optically transparent window.

As described herein, embodiments relate to improved dead zones and deadzone control for stereolithographic methods such as those related toCLIP. Accordingly, in some embodiments, the first wavelength of lightproduces a dead zone within said composition. As described herein, thetechnology provides a larger dead zone than extant technologies and thusthe present technology has improved printing speeds. In someembodiments, the technology produces a dead zone having a thickness thatis an order of magnitude larger than the dead zone thickness provided byextant technologies (extant technologies, e.g., comprising use of O₂inhibition, provide a dead zone of 100 μm to 1000 μm). For example, insome embodiments, the technology provides a dead zone having a width ofat least 0.5 mm (e.g., 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4,1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or more). In some embodiments, the deadzone has a width of at least 1 mm. In some embodiments, the technologyprovided herein produces a dead zone having a thickness of at leastapproximately 1 mm to 10 mm (e.g., at least approximately 1, 2, 3, 4, 5,6, 7, 8, 9, or 10 mm). In some embodiments, the technology providedherein produces a dead zone having a thickness that is greater than 10mm. In some embodiments, the increased dead zone thickness minimizesand/or eliminates problems related to resin reflow rates and associatedlimits on print speed.

In some embodiments, the first light source and second light source areconfigured to provide the second wavelength of light at a depth toactivate the photoinitiator deeper into the composition than the firstwavelength of light activates the photoinhibitor.

In some embodiments, systems comprise a component to produce patternedlight. In some embodiments, composition further comprises a lightabsorbing component. And, in some embodiments, systems further comprisea software object comprising instructions for producing said item.

Methods and systems described herein comprise providing or usingcompositions comprising a polymerizable monomer, a photoinitiator, and aphotoinhibitor. In some embodiments, the photoinhibitor has fast backreaction kinetics. In some embodiments, the photoinhibitor is a “precisephotoinhibitor”. In some embodiments, the photoinhibitor is a “precisephotoinhibitor” having fast back reaction kinetics. In some embodiments,the photoinitiator is a HABI compound. In some embodiments, thephotoinitiator is a bridged HABI compound.

The technology finds use in a wide range of applications. For example,in some embodiments, methods and systems find use in producing an itemcomprising a polymer.

Additional embodiments will be apparent to persons skilled in therelevant art based on the teachings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presenttechnology will become better understood with regard to the followingdrawings:

FIG. 1 shows the structure of tetraethylthiuram disulfide (“TED”) andthe reversible production of radicals from TED by light.

FIG. 2 shows the structure ofbis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide and the reversibleproduction of radicals frombis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide by light.

FIG. 3 shows the structure of an arylmethyl sulfone and the productionof radicals and sulfur dioxide from arylmethyl sulfone by light.

FIG. 4A shows a generic structure of a hexaarylbiimidazole (HABI)compound showing its dimeric structure comprising two imidazolylmoieties connected by a bond between the imidazole ring structures. Thebond can connect C to N, C to C, or N to N.

FIG. 4B shows the structure of a HABI compound and the reversibleproduction of radicals from the HABI compound by light.

FIG. 5A shows the structure of a generic bridged HABI compound. Thestructure shows the connection between imidazolyl moieties by an Rmoiety, which can be any chemical group or linkage to connect the twoimidazolyl moieties. The imidazolyl moieties are connected, in someembodiments, directly by a bond. The bond (curved line) between theimidazole ring structures can connect C to N, C to C, or N to N.

FIG. 5B shows the structure of a particular bridged HABI compound. Thestructure shows the connection between imidazolyl moieties by an Rmoiety, which can be any chemical group or linkage to connect the twoimidazolyl moieties. The imidazolyl moieties are connected, in someembodiments, directly by a bond. The bond between the imidazole ringstructures connects a C to an N.

FIG. 5C shows the structure of a particular bridged HABI compound. Thestructure shows a naphthalene bridging the imidazolyl moieties (e.g.,the R group is a naphthyl). The bond between the imidazole ringstructures connects a C to an N.

FIG. 5D shows the structure of a bridged HABI compound. The structureshows the connection between imidazolyl moieties by a bond. The bondbetween the imidazole ring structures connects C to C. Each of the Rgroups is independently selected from any substituent described herein.In some embodiments, the R is a methoxy.

FIG. 5E shows the structure of a bridged HABI compound. The structureshows the connection between imidazolyl moieties by a cyclophane.

FIG. 6 shows the structure of o-Cl-HABI and the reversible production ofradicals from o-Cl-HABI by light.

FIG. 7 is a plot showing the absorbance spectra of o-Cl-HABI (dottedline) and camphorquinone (solid line). One grey bar indicates the regionof the absorption maximum of approximately 470 nm for camphorquinone.Another grey bar shows a convenient range of wavelengths (e.g.,approximately 365 nm) within the transmission window of camphorquinoneat which o-Cl-HABI absorbs and that is consequently useful foractivation of o-Cl-HABI.

FIGS. 8A-8F show concurrent, two-color photoinitiation andphotoinhibition. FIG. 8A is a schematic of an embodiment of an opticalsystem for two-color, stereolithographic additive manufacturing (AM) byconcurrent photopolymerization and photoinhibition. Near UV (365 nm) issuperimposed onto patterned blue (458 nm) with a dichroic mirror andprojected through a transparent window into a photopolymerizable resinvat. FIGS. 8B to 8D show the structures of photoinitiator CQ (FIG. 8B),co-initiator EDAB (FIG. 8C), and photoinhibitor o-Cl-HABI (FIG. 8D).FIG. 8E shows a photograph of a solid block M (left) and a photograph ofa tug boat printed using the two-color, photopolymerization andphotoinhibition stereolithography system at 500 mm/hr and 375 mm/hr,respectively. FIG. 8F is a plot of data indicating that thepolymerization inhibition volume thickness is affected by varyingintensity ratios of the incident irradiation wavelengths(I_(UV,0)/I_(blue,0)) and resin absorbance (h_(UV)).

FIG. 9 is a plot showing the wavelength selective photoinitiation andtransient photoinhibition of methacrylate polymerization. The plot showsdata for methacrylate conversion versus time for bisGMA/TEGDMAformulated with CQ/EDAB and o-Cl-HABI under continuous irradiation with470 nm at 100 mW/cm² and intermittent irradiation with 365 nm at 30mW/cm² during the shaded periods as indicated. The accumulation oflophyl radicals during the 30 second UV irradiation periods afforddecreased polymerization rates. Upon cessation of UV irradiation, thepolymerization rates recover after induction times of approximately 30seconds owing to the relatively slow consumption of lophyl radicals byrecombination.

FIGS. 10A-E show the structures of (A) bisphenol A ethoxylate diacrylate(BPAEDA, n≈4); (B) triethylene glycol dimethacrylate (TEGDMA); (C)bisphenol A glycerolate dimethacrylate (bisGMA); (D) triethylene glycoldivinyl ether (TEGDVE); and (E) N-propylmaleimide (NPM).

FIGS. 10F-H are plots of data measured for alkene conversion versus timefor resin formulations of (F) bisGMA/TEGDMA, (G) BPAEDA, and (H)TEGDVE/NPM (vinyl ether and maleimide conversions denoted by solid anddashed lines, respectively) under continuous irradiation withexclusively 470 nm at 100 mW/cm² (black line, squares), 470 nm at 100mW/cm² and 365 nm at 10 mW/cm² (green line, triangles), 470 nm at 100mW/cm² and 365 nm at 30 mW/cm², (red line, circles), and 365 nm at 30mW/cm² (blue line, diamonds).

FIG. 11A is a schematic drawing of an embodiment of the technology usedfor intensity-patterned printing, e.g., using two-color photoinitiationand photoinhibition for controllable, far surface patterning of complex3D structures.

FIG. 11B shows use of variable intensity images to provide pixel-wisevariation of IUV,0/I_(blue,0) and the inhibition height.

FIG. 11C is a four-level intensity image of the University of Michiganseal.

FIG. 11D is a variable thickness part produced by a single,intensity-patterned exposure using the image in FIG. 11C.

FIG. 12A is a series of photographs showing argyle models printed usingtwo-color photoinitiation and photoinhibition to provide continuousprinting.

FIG. 12B is a plot showing cured thickness versus dosage of blue lightfor four acrylate-based resin formulations prepared with varying blue-5absorbing dye (Epolight 5675) loadings.

FIG. 12C is a plot showing maximum vertical print speeds achievable forvarying blue absorbance heights. All printing was done with I_(blue,0)of 110 mW/cm² and I_(UV,0) of 130 mW/cm² with h_(UV) of 125 μm.

FIG. 13 is a plot showing the effect of incident UV and blueillumination intensities on inhibition volume thickness andpolymerization rate. Adjustment of I_(UV,0)/I_(blue,0) along an isorateline allows for adjustment of the inhibition volume thickness whilemaintaining the same polymerization rate. Additionally, raisedpolymerization rates can be attained for a given inhibition volumethickness.

FIG. 14 is a plot of the UV-vis spectra of ultraviolet and blue lightabsorbers. The absorbance spectra of Tinuvin 328 and Epolight 5675(1.1×10⁻⁴ M and 1×10⁻² g/L, respectively) in isopropyl alcohol reveal noabsorbance by Tinuvin 328 in the visible region of the spectrum andrelatively low absorbance by Epolight 5675 in the near UV spectralregion, enabling their use to independently control resin absorbance inthe blue and near UV.

FIG. 15 shows the structures of triethylene glycol dimethacrylate(TEGDMA) and bisphenol A glycidyl methacrylate (bisGMA).

FIG. 16 is a plot showing wavelength-selective photoinitiation andphotoinhibition of radical-mediated, chain growth photopolymerization.Continuous irradiation with exclusively 470 nm at 50 mW/cm² (black line,squares), 470 nm at 50 mW/cm² and 365 nm at 30 mW/cm² (blue line,diamonds), and 365 nm at 30 mW/cm² (red line, circles).

FIG. 17 is a plot showing the wavelength selective photoinitiation andtransient photoinhibition of methacrylate polymerization by a bridgedHABI. Methacrylate conversion versus time for bisGMA/TEGDMA formulatedwith CQ/EDAB and bridged HABI (e.g., the “pincer” HABI shown in FIG. 5E)under continuous irradiation with 470 nm at 50 mW/cm² and intermittentirradiation with 365 nm at 30 mW/cm² during the shaded periods asindicated.

FIG. 18 shows a scheme of reactions following photolysis of butylnitrite.

FIG. 19 is a plot showing UV-visible absorbance spectra of CQ (solidblue line) and BN (dashed purple line) in THF. The near UV and visiblewavelengths used in the butyl nitrite examples are high-lighted.

FIGS. 20A-D are plots showing the wavelength-selective photoinitiationand photoinhibition of methacrylate-based bisGMA/TEGDMA formulations asmonitored by FTIR at BN concentrations of (A) 0% (control), (B) 0.5%,(C) 1%, and (D) 3% BN. Irradiation intensities are indicated in theinset for the data collected.

FIGS. 21A-D are plots showing the wavelength-selective photoinitiationand photoinhibition of acrylate-based TMPTA formulation as monitored byFTIR at BN concentrations of (A) 0% (control), (B) 0.5%, (C) 1%, and (D)3% BN. Irradiation intensities are indicated in the inset for the datacollected.

FIG. 22 is a plot showing Transient photoinhibition of TEGDMA/bisGMAusing continuous irradiation under blue light with intermittent near-UVexposure for 30 seconds (shaded intervals).

FIG. 23 is a schematic showing an embodiment 100 of the technology inwhich a composition 102 in a reaction vessel 101 is irradiated by afirst source providing a blue wavelength of light 107 and a secondsource providing a near-UV wavelength of light 103. The embodiment alsoshows two pattern (e.g., mask) components 104 and 108, a photoinhibitionregion 105 comprising a non-irradiated volume 106 within it, and aphotoinitiation region 109.

FIG. 24 shows a plot of initiating intensity (top plot, top line) andinhibiting intensity (top plot, bottom line) as a function of depth intoa composition (e.g., resin bath); and a plot of the ratio of initiatingand inhibiting intensities as a function of depth into a composition(e.g., resin bath) according to the technology provided herein (bottomplot).

FIG. 25A is a schematic of an embodiment of the technology providedherein. In FIG. 25A, an item 101 is being produced from a resincomposition 102 (e.g., comprising a polymerizable monomer, aphotoinitiator, and a photoinhibitor) according to an embodiment of thetechnology provided herein. A build support plate 103 is attached to theitem 101 and draws it up from the resin composition 102. A firstwavelength of light 104 (dotted lines) and a second wavelength of light105 (solid lines) irradiate the resin composition 102 through anoptically transparent window 106. The first wavelength of light 104 hasa wavelength and intensity to activate the photoinhibitor (e.g., toproduce an inhibiting species (e.g., an inhibiting radical) in thecomposition. The second wavelength of light 105 has a wavelength andintensity to activate the photoinitiator (e.g., to produce an initiatingspecies (e.g., an initiating radical) in the composition. The firstwavelength of light 104 activates the photoinhibitor to produce the deadzone 107 as shown in FIG. 25B.

FIG. 25B shows a schematic enlargement of a region of the schematicshown in FIG. 25A. The plot at the left shows the intensity of theinitiating wavelength (solid line), the intensity of the inhibitingwavelength (dashed line), and the polymerization reaction rate (dot-dashline) within the composition 102 shown at the right as a function ofdistance from the optically transparent window 106. The vertical axisshows distance (in arbitrary units appropriate to scale for a CLIP-typeapparatus) from the optically transparent window 106 up through theresin composition 102 in the direction of the build support plate 103.The origin of the vertical axis is at the outside surface of theoptically transparent window 106 upon which the first wavelength oflight 104 (dotted lines) and second wavelength of light 105 (solidlines) impinge prior to passing through the optically transparent window106 to irradiate the resin composition 102. The horizontal axis showsthe intensities of the initiating wavelength (solid line) and theinhibiting wavelength (dashed line) with the origin at zero (0). Theintensities of the initiating and inhibiting wavelengths are highestprior to and when passing through the optically transparent window 106and decrease to zero as the initiating and inhibiting wavelengths passthrough the resin composition 102. The horizontal axis also shows therelative polymerization reaction rate (dash-dot line) producing thepolymer with the origin at (zero). The dead zone 107 is the region wherephotoinhibition occurs within the resin composition such that thepolymerizable monomers do not polymerize. Above the dead zone 107,polymerization occurs where inhibition does not inhibit polymerizationand the initiating intensity is sufficient to activate thephotoinitiator (e.g., to produce an initiating species (e.g., aninitiating radical)).

FIG. 26 shows an apparatus and/or system according to embodiments of thetechnology provided herein. The apparatus comprises a resin bath in areaction vessel comprising a projection window (e.g., an opticallytransparent window). A blue light source (a DLP) and a UV light sourcesimultaneously irradiate the composition through the opticallytransparent window. A short pass dichroic mirror is used to combine theblue and UV wavelengths for irradiation of the composition.

It is to be understood that the figures are not necessarily drawn toscale, nor are the objects in the figures necessarily drawn to scale inrelationship to one another. The figures are depictions that areintended to bring clarity and understanding to various embodiments ofapparatuses, systems, and methods disclosed herein. Wherever possible,the same reference numbers will be used throughout the drawings to referto the same or like parts. Moreover, it should be appreciated that thedrawings are not intended to limit the scope of the present teachings inany way.

DETAILED DESCRIPTION

Provided herein is technology relating to producing polymers andparticularly, but not exclusively, to methods and systems for producingarticles using three-dimensional printing. Provided herein is technologyrelating to polymerization and particularly, but not exclusively, tomethods, systems, and compositions for improving control ofpolymerization using a polymerization photoinhibitor having fast backreaction kinetics such as hexaarylbiimidazole compounds and bridgedhexaarylbiimidazole compounds.

In this detailed description of the various embodiments, for purposes ofexplanation, numerous specific details are set forth to provide athorough understanding of the embodiments disclosed. One skilled in theart will appreciate, however, that these various embodiments may bepracticed with or without these specific details. In other instances,structures and devices are shown in block diagram form. Furthermore, oneskilled in the art can readily appreciate that the specific sequences inwhich methods are presented and performed are illustrative and it iscontemplated that the sequences can be varied and still remain withinthe spirit and scope of the various embodiments disclosed herein.

All literature and similar materials cited in this application,including but not limited to, patents, patent applications, articles,books, treatises, and internet web pages are expressly incorporated byreference in their entirety for any purpose. Unless defined otherwise,all technical and scientific terms used herein have the same meaning asis commonly understood by one of ordinary skill in the art to which thevarious embodiments described herein belongs. When definitions of termsin incorporated references appear to differ from the definitionsprovided in the present teachings, the definition provided in thepresent teachings shall control. The section headings used herein arefor organizational purposes only and are not to be construed as limitingthe described subject matter in any way.

Definitions

To facilitate an understanding of the present technology, a number ofterms and phrases are defined below. Additional definitions are setforth throughout the detailed description.

Throughout the specification and claims, the following terms take themeanings explicitly associated herein, unless the context clearlydictates otherwise. The phrase “in one embodiment” as used herein doesnot necessarily refer to the same embodiment, though it may.Furthermore, the phrase “in another embodiment” as used herein does notnecessarily refer to a different embodiment, although it may. Thus, asdescribed below, various embodiments of the invention may be readilycombined, without departing from the scope or spirit of the invention.

In addition, as used herein, the term “or” is an inclusive “or” operatorand is equivalent to the term “and/or” unless the context clearlydictates otherwise. The term “based on” is not exclusive and allows forbeing based on additional factors not described, unless the contextclearly dictates otherwise. In addition, throughout the specification,the meaning of “a”, “an”, and “the” include plural references. That is,the singular forms “a,” “and,” and “the” include plural referents unlessthe context clearly dictates otherwise. Thus, for example, reference to“a polymer” may include more than one polymer. The meaning of “in”includes “in” and “on.”

As used herein, the terms “about”, “approximately”, “substantially”, and“significantly” are understood by persons of ordinary skill in the artand will vary to some extent on the context in which they are used. Ifthere are uses of these terms that are not clear to persons of ordinaryskill in the art given the context in which they are used, “about” and“approximately” mean plus or minus less than or equal to 10% of theparticular term and “substantially” and “significantly” mean plus orminus greater than 10% of the particular term.

As used herein, spatially relative terms, such as “under,” “below,”“lower,” “over,” “upper”, “left”, “right”, and the like are used forease of description to describe relationships between components,elements, features, etc., e.g., as illustrated in a figure. Spatiallyrelative terms are intended to encompass different orientations ofembodiments of the technology in use or operation, e.g., in addition tothe orientation as depicted in the figures. For example, elementsdescribed as “under” or “beneath” other elements or features would thenbe oriented “over” the other elements or features when the positions ofelements are changed in some embodiments.

As used herein, the term “optional” or “optionally” means that thesubsequently described circumstance may or may not occur and is notnecessary, so that the description includes instances where thecircumstance occurs and instances where it does not occur.

As used herein, the term “polymer” refers to a macromolecule formed bythe chemical union of monomers (e.g., polymerizable monomers). In someembodiments, a polymer comprises two, three, four, five, or moremonomers. The term polymer includes homopolymer and copolymer blockcopolymers, and polymers of any topology including star polymers, blockcopolymers, gradient copolymers, periodic copolymers, telechelicpolymers, bottle-brush copolymers, random copolymers, statisticalcopolymers, alternating copolymers, graft polymers, branched orhyperbranched polymers, comb polymers, such polymers tethered fromparticle surfaces, as well as other polymer structures.

As used herein, the term “moiety” refers to one of two or more partsinto which something may be divided, such as, for example, the variousparts of a molecule or a chemical group.

The term “alkyl” as used herein is a branched or unbranched saturatedhydrocarbon group of 1 to 24 carbon atoms, for example 1 to 12 carbonatoms or 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl,s-pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, dode cyl,tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. The alkylgroup can also be substituted or unsubstituted. The alkyl group can besubstituted with one or more groups including, but not limited to,substituted or unsubstituted alkyl, cycloalkyl, alkoxy, amino, ether,halide, hydroxy, nitro, silyl, sulfo-oxo, or thiol, as described herein.A “lower alkyl” group is an alkyl group containing from one to sixcarbon atoms.

Throughout the specification “alkyl” is generally used to refer to bothunsubstituted alkyl groups and substituted alkyl groups; however,substituted alkyl groups are also specifically referred to herein byidentifying the specific substituent(s) on the alkyl group. For example,the term “halogenated alkyl” specifically refers to an alkyl group thatis substituted with one or more halide, e.g., fluorine, chlorine,bromine, or iodine. The term “alkoxyalkyl” specifically refers to analkyl group that is substituted with one or more alkoxy groups, asdescribed below. The term “alkylamino” specifically refers to an alkylgroup that is substituted with one or more amino groups, as describedbelow, and the like. When “alkyl” is used in one instance and a specificterm such as “alkylalcohol” is used in another, it is not meant to implythat the term “alkyl” does not also refer to specific terms such as“alkylalcohol” and the like.

This practice is also used for other groups described herein. That is,while a term such as “cycloalkyl” refers to both unsubstituted andsubstituted cycloalkyl moieties, the substituted moieties can, inaddition, be specifically identified herein; for example, a particularsubstituted cycloalkyl can be referred to as, e.g., an“alkylcycloalkyl.” Similarly, a substituted alkoxy can be specificallyreferred to as, e.g., a “halogenated alkoxy,” a particular substitutedalkenyl can be, e.g., an “alkenylalcohol,” and the like. Again, thepractice of using a general term, such as “cycloalkyl,” and a specificterm, such as “alkylcycloalkyl,” is not meant to imply that the generalterm does not also include the specific term.

The term “cycloalkyl” as used herein is a non-aromatic carbon-based ringcomposed of at least three carbon atoms. Examples of cycloalkyl groupsinclude, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, norbornyl, and the like. The term “heterocycloalkyl” is atype of cycloalkyl group as defined above, and is included within themeaning of the term “cycloalkyl,” where at least one of the carbon atomsof the ring is replaced with a heteroatom such as, but not limited to,nitrogen, oxygen, sulfur, or phosphorus. The cycloalkyl group andheterocycloalkyl group can be substituted or unsubstituted. Thecycloalkyl group and heterocycloalkyl group can be substituted with oneor more groups including, but not limited to, substituted orunsubstituted alkyl, cycloalkyl, alkoxy, amino, ether, halide, hydroxy,nitro, silyl, sulfo-oxo, or thiol as described herein,

The term “polyalkylene group” as used herein is a group having two ormore CH₂ groups linked to each other. The polyalkylene group can also berepresented by the formula —(CH₂)_(n)— where “n” is an integer of from 2to 500.

The terms “alkoxy” and “alkoxyl” are used herein to refer to an alkyl orcycloalkyl group bonded through an ether linkage; that is, an “alkoxy”group can be defined as—OA1 where A1 is alkyl or cycloalkyl as definedabove. “Alkoxy” also includes polymers of alkoxy groups as justdescribed; that is, an alkoxy can be a polyether such as —OA1-OA2 or—OA1-(OA2)_(n)-OA3, where “n” is an integer of from 1 to 200 and A1, A2,and A3 are alkyl and/or cycloalkyl groups.

The term “alkenyl” as used herein is a hydrocarbon group of from 2 to 24carbon atoms with a structural formula containing at least onecarbon-carbon double bond. Asymmetric structures such as (A1A2)C═C(A3A4)are intended to include both the E and Z isomers. This can be presumedin structural formulae herein wherein an asymmetric alkene is present,or it can be explicitly indicated by the bond symbol C═C. The alkenylgroup can be substituted with one or more groups including, but notlimited to, substituted or unsubstituted alkyl, cycloalkyl, alkoxy,alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl,aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone,azide, nitro, silyl, sulfo-oxo, or thiol, as described herein.

The term “cycloalkenyl” as used herein is a non-aromatic carbon-basedring composed of at least three carbon atoms and containing at least onecarbon-carbon double bound as represented in some embodiments as C═C.Examples of cycloalkenyl groups include, but are not limited to,cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadienyl,cyclohexenyl, cyclohexadienyl, norbomenyl, and the like. The term“heterocycloalkenyl” is a type of cycloalkenyl group as defined above,and is included within the meaning of the term “cycloalkenyl,” where atleast one of the carbon atoms of the ring is replaced with a heteroatomsuch as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus.The cycloalkenyl group and heterocycloalkenyl group can be substitutedor unsubstituted. The cycloalkenyl group and heterocycloalkenyl groupcan be substituted with one or more groups including, but not limitedto, substituted or unsubstituted alkyl, cycloalkyl, alkoxy, alkenyl,cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl, aldehyde, amino,carboxylic acid, ester, ether, halide, hydroxy, ketone, azide, nitro,silyl, sulfo-oxo, or thiol as described herein.

The term “alkynyl” as used herein is a hydrocarbon group of 2 to 24carbon atoms with a structural formula containing at least onecarbon-carbon triple bond. The alkynyl group can be unsubstituted orsubstituted with one or more groups including, but not limited to,substituted or unsubstituted alkyl, cycloalkyl, alkoxy, alkenyl,cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl, aldehyde, amino,carboxylic acid, ester, ether, halide, hydroxy, ketone, azide, nitro,silyl, sulfo-oxo, or thiol, as described herein.

The term “cycloalkynyl” as used herein is a non-aromatic carbon-basedring composed of at least seven carbon atoms and containing at least onecarbon-carbon triple bound. Examples of cycloalkynyl groups include, butare not limited to, cycloheptynyl, cyclooctynyl, cyclononynyl, and thelike. The term “heterocycloalkynyl” is a type of cycloalkenyl group asdefined above, and is included within the meaning of the term“cycloalkynyl,” where at least one of the carbon atoms of the ring isreplaced with a heteroatom such as, but not limited to, nitrogen,oxygen, sulfur, or phosphorus. The cycloalkynyl group andheterocycloalkynyl group can be substituted or unsubstituted. Thecycloalkynyl group and heterocycloalkynyl group can be substituted withone or more groups including, but not limited to, substituted orunsubstituted alkyl, cycloalkyl, alkoxy, alkenyl, cycloalkenyl, alkynyl,cycloalkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester,ether, halide, hydroxy, ketone, azide, nitro, silyl, sulfo-oxo, or thiolas described herein.

The term “aryl” as used herein is a group that contains any carbon-basedaromatic group including, but not limited to, benzene, naphthalene,phenyl, biphenyl, phenoxybenzene, and the like. The term “aryl” alsoincludes “heteroaryl,” which is defined as a group that contains anaromatic group that has at least one heteroatom incorporated within thering of the aromatic group. Examples of heteroatoms include, but are notlimited to, nitrogen, oxygen, sulfur, and phosphorus. Likewise, the term“non-heteroaryl,” which is also included in the term “aryl,” defines agroup that contains an aromatic group that does not contain aheteroatom. The aryl group can be substituted or unsubstituted. The arylgroup can be substituted with one or more groups including, but notlimited to, substituted or unsubstituted alkyl, cycloalkyl, alkoxy,alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl,aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone,azide, nitro, silyl, sulfo-oxo, or thiol as described herein. The term“biaryl” is a specific type of aryl group and is included in thedefinition of “aryl.” Biaryl refers to two aryl groups that are boundtogether via a fused ring structure, as in naphthalene, or are attachedvia one or more carbon-carbon bonds, as in biphenyl.

The term “aldehyde” as used herein is represented by the formula —C(O)H.Throughout this specification “C(O)” is a short hand notation for acarbonyl group, represented in some embodiments as C═O.

The terms “amine” or “amino” as used herein are represented by theformula NA1A2A3, where A1, A2, and A3 can be, independently, hydrogen orsubstituted or unsubstituted alkyl, cycloalkyl, alkenyl, cycloalkenyl,alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein,

The term “carboxylic acid” as used herein is represented by the formula—C(O)OH.

The term “ester” as used herein is represented by the formula —OC(O)A1or —C(O)OA1, where A1 can be a substituted or unsubstituted alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, orheteroaryl group as described herein. The term “polyester” as usedherein is represented by the formula -(A1O(O)C-A2-C(O)O)a- or-(A1O(O)C-A2-OC(O))_(n)—, where A1 and A2 can be, independently, asubstituted or unsubstituted alkyl, cycloalkyl, alkenyl, cycloalkenyl,alkynyl, cycloalkynyl, aryl, or heteroaryl group described herein and“n” is an integer from 1 to 500. “Polyester” is as the term used todescribe a group that is produced by the reaction between a compoundhaving at least two carboxylic acid groups with a compound having atleast two hydroxyl groups.

The term “ether” as used herein is represented by the formula A1OA2,where A1 and A2 can be, independently, a substituted or unsubstitutedalkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl,or heteroaryl group described herein. The term “polyether” as usedherein is represented by the formula -(A1O-A2O)_(n)—, where A1 and A2can be, independently, a substituted or unsubstituted alkyl, cycloalkyl,alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl groupdescribed herein and “n” is an integer of from 1 to 500. Examples ofpolyether groups include polyethylene oxide, polypropylene oxide, andpolybutylene oxide.

The term “halide” as used herein refers to the halogens fluorine,chlorine, bromine, and iodine.

The term “hydroxyl” as used herein is represented by the formula —OH.

The term “ketone” as used herein is represented by the formula A1C(O)A2,where A1 and A2 can be, independently, a substituted or unsubstitutedalkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl,or heteroaryl group as described herein,

The term “azide” as used herein is represented by the formula —N₃.

The term “nitro” as used herein is represented by the formula —NO₂.

The term “nitrile” as used herein is represented by the formula —CN.

The term “sulfo-oxo” as used herein is represented by the formulas—S(O)A1, —S(O)2A1, —OS(O)2A1, or —OS(O)2OA1, where A1 can be hydrogen ora substituted or unsubstituted alkyl, cycloalkyl, alkenyl, cycloalkenyl,alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein.Throughout this specification “S(O)” is a short hand notation for S═O.The term “sulfonyl” is used herein to refer to the sulfo-oxo grouprepresented by the formula —S(O)2A1, where A1 can be hydrogen or asubstituted or unsubstituted alkyl, cycloalkyl, alkenyl, cycloalkenyl,alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein.The term “sulfone” as used herein is represented by the formulaA1S(O)2A2, where A1 and A2 can be, independently, a substituted orunsubstituted alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl,cycloalkynyl, aryl, or heteroaryl group as described herein. The term“sulfoxide” as used herein is represented by the formula A1S(O)A2, whereA1 and A2 can be, independently, a substituted or unsubstituted alkyl,cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, orheteroaryl group as described herein.

The term “thiol” as used herein is represented by the formula —SH.

As used herein, the term “alkylacrylic acid” refers to acrylic acid,alkyl-substituted acrylic acids, salts thereof, and derivatives thereof.In one aspect, an alkylacrylic acid can be further substituted. In afurther aspect, an alkylacrylic acid is methacrylic acid.

As used herein, the term “sterically hindered” refers to a tertiary orquaternary substituted moiety wherein at least one of the substituentshas at least two carbon atoms. For example, a sterically hindered moietycan have the structure: wherein A1 is a carbon atom or silicon atom andwherein at least one of A2, A3, and A4 is an organic group having atleast two carbon atoms. In a further aspect, at least one of A2, A3, andA4 is methyl, and at least one of A2, A3, and A4 is an organic grouphaving at least two carbon atoms.

The term “inert” to refer to a substituent or compound means that thesubstituent or compound will not undergo modification either (1) in thepresence of reagents that will likely contact the substituent orcompound, or (2) under conditions that the substituent or compound willlikely be subjected to (e.g., chemical processing carried out subsequentto attachment an “inert” moiety to a substrate surface).

As used herein, the term “substituted” is contemplated to include allpermissible substituents of organic compounds. In a broad aspect, thepermissible substituents include acyclic and cyclic, branched andunbranched, carbocyclic and heterocyclic, and aromatic and nonaromaticsubstituents of organic compounds. Illustrative substituents include,for example, those described below. The permissible substituents can beone or more and the same or different for appropriate organic compounds.For purposes of this disclosure, the heteroatoms, such as nitrogen, canhave hydrogen substituents and/or any permissible substituents oforganic compounds described herein which satisfy the valences of theheteroatoms. This disclosure is not intended to be limited in any mannerby the permissible substituents of organic compounds. Also, the terms“substitution” or “substituted with” include the implicit proviso thatsuch substitution is in accordance with permitted valence of thesubstituted atom and the substituent, and that the substitution resultsin a stable compound, e.g., a compound that does not spontaneouslyundergo transformation such as by rearrangement, cyclization,elimination, etc.

As used herein, the term “radical” refers to an atom, molecule, or ionthat has an unpaired valence electron. For instance, in someembodiments, a “radical” is a small molecule comprising one (sometimestwo) unpaired electron on an atom or functional group. In someembodiments, a radical is formed by homolytic cleavage of a bond. Asused herein, the terms “radical” and “free radical” are equivalent.

As used herein, a “photoinitiator” is a molecule that produces radicalsafter irradiation with light to initiate polymerization of apolymerizable monomer. Free radical photoinitiators are known in theart. These photoinitiators absorb energy in varying ranges in the UVspectrum (100-450 nm), including UV A (320-400 nm), UV B (280-320 nm),UV C (200-280 nm), deep UV (100-200 nm) and near-visible UV (400-450 nm,also known as UV-VIS) and produce a free radical reactive species, whichthen initiates polymerization of the polymerizable monomers. See, e.g.,W. Arthur Green, “Industrial Photoinitators: A Technical Guide,” CRCPress, 2010. In some embodiments, the free radical photoinitiators areactivated in the visible spectrum, e.g., at wavelengths up to 600 or 700nm.

As used herein, a “photoinhibitor” is a molecule that produces aninhibiting species after irradiation with light to minimize, inhibit,prevent, and/or terminate polymerization of a polymerizable monomer. Insome embodiments, a photoinhibitor forms a radical that minimizes,inhibits, prevents, and/or terminates polymerization of a polymerizablemonomer. However, a photoinhibitor need not produce radicals; thus, insome embodiments, a photoinhibitor produces, e.g., an inhibiting speciesthat is, e.g., a non-radical molecular fragment or an isomer thatinhibits polymerizations (e.g., radical polymerizations). Aphotoinhibitor absorbs energy in varying ranges in the UV spectrum(100-450 nm), including UV A (320-400 nm), UV B (280-320 nm), UV C(200-280 nm), deep UV (100-200 nm) and near-visible UV (400-450 nm, alsoknown as UV-VIS) and produces an inhibiting species, which then inhibitspolymerization of the polymerizable monomers. In some embodiments, thephotoinhibitors are activated in the visible spectrum, e.g., atwavelengths up to 600 or 700 nm.

As used herein, the term “precise photoinhibitor” refers to aphotoinhibitor for which the non-photoactivated form of thephotoinhibitor does not inhibit or retard a polymerization ofpolymerizable monomers, for which the non-photoactivated form of thephotoinhibitor does not initiate polymerization of polymerizablemonomers, for which the photoactivated form of the photoinhibitor (e.g.,inhibiting species) inhibits the polymerization of polymerizablemonomers, and for which the photoactivated form of the photoinhibitor(e.g., inhibiting species) does not initiate polymerization ofpolymerizable monomers. In some embodiments, a precise photoinhibitorhas a fast back reaction.

As used herein, the terms “back reaction” or “thermal back reaction”refer to the reformation of the photoinhibitor or photoinitiatormolecule from their products (e.g., radicals), e.g., the productsproduced from the photoinhibitor or photoinitiator by irradiation.

As used herein, the term “fast reaction” refers to a chemical reaction(e.g., a back reaction) that has fast reaction kinetics. As used herein,the term “fast reaction kinetics” refers to a chemical reaction thatdepletes a compound such that the compound has a half-life ofapproximately 100 ns to 100 μs to 100 ms to 100 s (e.g., 10, 20, 30, 40,50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000ns; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600,700, 800, 900, or 1000 μs; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200,300, 400, 500, 600, 700, 800, 900, or 1000 ms; or 0, 20, 30, 40, 50, 60,70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 s). Insome embodiments, a fast reaction (e.g., a fast back reaction) reforms acompound (e.g., a photoactivatable compound (e.g., a photoinhibitor, aphotoinitiator)) from its products (e.g., an inhibiting species (e.g.,inhibiting radical)) with fast kinetics. In particular embodiments, afast reaction reforms an inactive form of a photoinhibitor from theinhibiting species (e.g., inhibiting radical) with fast reactionkinetics such that an amount or concentration of the inhibiting species(e.g., inhibiting radical) that is effective in inhibitingpolymerization of the polymerizable monomer is only present in a regionirradiated by an intensity and/or wavelength of light that activates thephotoinhibitor to form the inhibiting species (e.g., inhibitingradical).

As used herein, the term “light” is understood to refer toelectromagnetic radiation in any appropriate region of theelectromagnetic spectrum and is not limited to visible light.Accordingly, the term “light” encompasses infrared, ultraviolet, andvisible electromagnetic radiation. As used herein, the term“irradiation” refers to light directed toward a surface, composition,molecule, etc., so that it contacts the surface, composition, molecule,etc. As used herein, the term “blue light” refers to light having awavelength in the range of approximately 450-495 nm. As used herein, “UVlight” refers to light having a wavelength of approximately 100-450 nm.

In some embodiments, an “activating” intensity of light is lightprovided above a threshold intensity required to effect a chemicalreaction. For example, in some embodiments light provided at anactivating intensity forms an initiating radical from a photoinitiatoror forms an inhibiting radical from a photoinhibitor. In someembodiments, an activating intensity of light is expressed as theintensity of irradiation at a particular wavelength of electromagneticradiation or an average irradiation over a particular range ofwavelengths of electromagnetic radiation. In some embodiments, the“activating” intensity is expressed as a number of photons (e.g.,photons of a particular wavelength) absorbed by a photoactivatablemolecule. In some embodiments, the “activating” intensity is expressedin units of irradiance or intensity, e.g., in the form of power per unitarea (e.g., W/cm² or the like). In some embodiments, the activatingintensity is expressed as an irradiance at the absorption maximum of aphotoactivatable molecule. However, the activating light need not beprovided at a wavelength at or near the absorption maximum (e.g.,wavelength of maximal absorption) of a photoactivatable molecule; thus,in some embodiments, the activating light is provided at a wavelength atwhich the absorption by the photoactivatable molecule of said wavelengthis less than 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2,or 1% of the absorption by the molecule at the wavelength of theabsorption maximum.

As used herein, the term “photon” refers to a unit particle ofelectromagnetic energy.

As used herein, the term “color” or “wavelength” is used interchangeablywith the term “spectrum.” However, the term, “color” generally is usedto refer to a property of electromagnetic radiation that is perceivableby an observer (though this usage is not intended to limit the scope ofthis term). Accordingly, the term “different colors” implies twodifferent spectra with different wavelengths, wavelength components,wavelength ranges, spectra, and/or bandwidths. In addition, “color” maybe used to refer to white and non-white light.

As used herein, the terms “photon beam”, “light beam”, “electromagneticbeam”, “image beam”, or “beam” refer to a somewhat localized (in timeand space) beam or bundle of photons or electromagnetic waves of variousfrequencies or wavelengths within the electromagnetic spectrum.

As used herein, the terms “light source”, “photon source”, or “source”refer to various devices that are capable of emitting, providing,transmitting, or generating one or more photons or electromagnetic wavesof one or more wavelengths or frequencies within the electromagneticspectrum. A light or photon source may transmit one or more outgoinglight beams. A photon source may be a laser, a light emitting diode(LED), a light bulb, or the like. A photon source may generate photonsvia stimulated emissions of atoms or molecules, an incandescent process,or various other mechanisms that generate an electromagnetic wave or oneor more photons. A photon source may provide continuous or pulsedoutgoing light beams of a predetermined frequency, range of frequencies,wavelength, range of wavelengths, or spectra. The outgoing light beamsmay be coherent light beams. The photons emitted by a light source maybe of various wavelengths or frequencies.

As used herein, the term “dead zone” refers to a layer of polymerizablemonomer that does not polymerize, e.g., due to the presence of a speciesthat inhibits polymerization of the polymerizable monomer. That is, the“dead zone” is a layer of unpolymerized composition adjacent to thepolymerized item. In some embodiments, the dead zone comprises aninhibitor of polymerization (at least in a polymerization-inhibitingamount) and in an adjacent layer, the inhibitor is not present (e.g., ispresent in less than a polymerization-inhibiting amount), e.g., becausethe inhibitor has been consumed, has not been produced, or has not movedto the adjacent layer. The technology is not limited in the shape of thedead zone. For example, in some embodiments, the dead zone has a regularshape (e.g., a rectangular prism or “slab” of the composition comprisingthe polymerizable monomer). In some embodiments, the dead zone has anirregular shape (e.g., the dead zone has a contoured “topology” at theinterface with the adjacent layer). In some embodiments, the shape ofthe dead zone is produced by projecting a two-dimensional imagecomprising varied intensities (e.g., at the pixel level) of thewavelength of light that activates the photoinhibitor (e.g., thatproduces the inhibiting species from the photoinhibitor).

As used herein, a “large cross section” and/or a “large cross-sectionalarea” refers to a cross-section having an area of approximately 1 to 10cm² (e.g., 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8,8.5, 9, 9.5, or 10 cm²).

Description

Provided herein is technology relating to polymerization andparticularly, but not exclusively, to methods, systems, and compositionsfor improving control of polymerization using a polymerizationphotoinhibitor having fast back reaction kinetics such ashexaarylbiimidazole compounds and bridged hexaarylbiimidazole compounds.The technology has several advantages. For example, the polymerizationtechnology is not susceptible to polymerization-retarding chain transferreactions, in contrast to technologies that comprise use of compoundsthat participate extensively in chain transfer reactions, e.g., TED,bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide, etc. Further, thetechnology comprises use of photoinhibitor compounds that absorb atwavelength ranges that are compatible and complementary with manyphotoinitiation sensitizers. The present technology does not compriseuse of compounds that release small molecules upon photocleavage, e.g.,gases or other compounds that compromise polymerized structures. Asdescribed herein, photocleavage of the photoinhibitors is reversible andreformation of the photoinhibitor compound has fast back reactionkinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)).

Although the disclosure herein refers to certain illustratedembodiments, it is to be understood that these embodiments are presentedby way of example and not by way of limitation.

Hexaarylbiimidazole (HABI) Compounds

In some embodiments, the technology relates to the use of ahexaarylbiimidazole (HABI) compound as a photoactivated inhibitor ofpolymerization (“photoinhibitor”). Hexaarylbiimidazole (HABI) wasdeveloped in the 1960s as a photochromic molecule by Hayashi and Maeda(see, e.g., Hayashi and Maeda (1960) “Preparation of a new phototropicsubstance” Bull. Chem. Soc. Jpn. 33(4): 565-66, incorporated herein byreference). The general structure of a HABI compound is shown in FIG. 4Aand one particular HABI compound is shown on the left in FIG. 4B. FIG.4B shows: i) the light-induced homolytic cleavage of the HABI C—N bondto produce two radicals (e.g., triphenylimidazolyl radicals (“TPIR”),also known as lophyl radicals); and ii) recombination of the tworadicals in the “back reaction” to reform the HABI imidazole dimer(accordingly, also called a triphenylimidazolyl dimer “TPID”). Therecombination “back reaction” is driven by thermal energy and radicaldiffusion. The lophyl radical has a large absorption band in the visibleregion of the electromagnetic spectrum, whereas HABI absorbs strongly inthe UV region and weakly in the blue region of the electromagneticspectrum and is therefore either colorless or yellow. Consequently, HABIgenerates a colored radical species upon UV light irradiation and theradicals slowly reform to produce the colorless HABI imidazole dimerwhen light irradiation is stopped. FIG. 6 showso-chlorohexaarylbiimidazole (o-Cl-HABI), the light-induced reactionforming the chloro-triphenylimidizolyl radicals, and the thermallydriven back reaction to reform the o-Cl-HABI. The halflife of theradicals formed in this reaction is approximately tens of seconds (e.g.,approximately 10 s). Thus, in some embodiments, the technology relatesto an o-chlorohexaarylbiimidazole (o-Cl-HABI) that has a half-life ofapproximately tens of seconds (e.g., approximately 10 s).

Cleavage of the HABI C—N bond by UV irradiation occurs in less than 100fs and is thus nearly (e.g., substantially, effectively) instantaneous;recombination of the radicals to reform HABI is a second order reactionthat occurs over a time of up to a few minutes at room temperature.Thus, the lophyl radicals formed from HABI have a half-life of tens ofseconds to several (e.g., 5 to 10 or more) minutes (see, e.g., Satoh etal. (2007) “Ultrafast laser photolysis study on photodissociationdynamics of a hexaarylbiimidazole derivative” Chem. Phys. Lett. 448(4-6): 228-31; Sathe, et al. (2015) “Re-examining the PhotomediatedDissociation and Recombination Kinetics of Hexaarylbiimidazoles” Ind.Eng. Chem. Res. 54 (16): 4203-12, each of which is incorporated hereinby reference). HABI has been known as a photoinitiator, e.g., forimaging and photoresists. HABI compounds do not initiate on their ownupon formation of radicals. When used as a photoinitiator, the radicalabstracts hydrogen atoms from coinitiator thiol groups (e.g., a crystalviolet precursor) to form an initiating moiety. See, e.g., Dessauer, R.(2006) Photochemistry History and Commercial Applications ofHeaarylbiimidazoles, Elsevier.

As noted above, HABI compounds do not exhibit photoinitiation activitywhen irradiated. Moreover, HABI compounds do not participate in chaintransfer reactions and thus polymerization rates are not inherentlyretarded by the presence of HABI compounds. Finally, HABI compoundstypically exhibit very weak absorbance in the blue region of theelectromagnetic spectrum and moderately absorb in the near-UV region ofthe electromagnetic spectrum, thus complementing the absorbance spectrumof several photoinitiators activated by blue light.

In some embodiments, the technology relates to use of a bridged HABI.See, e.g., Iwahori et al. (2007) “Rational design of a new class ofdiffusion-inhibited HABI with fast back-reaction” J Phys Org Chem 20:857-63; Fujita et al. (2008) “Photochromism of a radicaldiffusion-inhibited hexaarylbiimidazole derivative with intensecoloration and fast decoloration performance” Org Lett 10: 3105-08;Kishimoto and Abe (2009) “A fast photochromic molecule that colors onlyunder UV light” J Am Chem Soc 131: 4227-29; Harada et al. (2010)“Remarkable acceleration for back-reaction of a fast photochromicmolecule” J Phys Chem Lett 1: 1112-15; Mutoh et al. (2010) “An efficientstrategy for enhancing the photosensitivity of photochromic[2.2]paracyclophane-bridged imidazole dimers” J Photopolym Sci Technol23: 301-06; Kimoto et al. (2010) “Fast photochromic polymers carrying[2.2]paracyclophane-bridged imidazole dimer” Macromolecules 43: 3764-69;Hatano et al. (2010) “Unprecedented radical-radical reaction of a[2.2]paracyclophane derivative containing an imidazolyl radical moiety”Org Lett 12: 4152-55; Hatano et al. (2011) “Reversible photogenerationof a stable chiral radical-pair from a fast photochromic molecule” JPhys Chem Lett 2: 2680-82; Mutoh and Abe (2011) “Comprehensiveunderstanding of structure-photosensitivity relationships ofphotochromic [2.2]paracyclophane-bridged imidazole dimers” J Phys Chem A115: 4650-56; Takizawa et al. (2011) “Photochromic organogel based on[2.2]paracyclophane-bridged imidazole dimer with tetrapodal ureamoieties” Dyes Pigm 89: 254-59; Mutoh and Abe (2011) “Photochromism of awater-soluble vesicular [2.2]paracyclophane bridged imidazole dimer”Chem Comm 47:8868-70; Yamashita and Abe (2011) “Photochromic propertiesof [2.2]paracyclophane-bridged imidazole dimer with increasedphotosensitivity by introducing pyrenyl moiety” J Phys Chem A 115:13332-37; Kawai et al. (2012) “Entropy-controlled thermal back-reactionof photochromic [2.2]paracyclophane-bridged imidazole dimer” Dyes Pigm92: 872-76; Mutoh et al. (2012) “Spectroelectrochemistry of aphotochromic [2.2]paracyclophane-bridged imidazole dimer: Clarificationof the electrochemical behavior of HABI” J Phys Chem A 116: 6792-97;Mutoh et al. (2013) “Photochromism of a naphthalene-bridged imidazoledimer constrained to the ‘anti’ conformation” Org Lett 15: 2938-41;Shima et al. (2014) “Enhancing the versatility and functionality of fastphotochromic bridged-imidazole dimers by flipping imidazole ring” J AmChem Soc 136: 3796-99; Iwasaki et al. (2014) “A chiral BINOL-bridgedimidazole dimer possessing sub-millisecond fast photochromism” ChemCommun 50: 7481-84; and Yamaguchi et al. (2015) “Nanosecond photochromicmolecular switching of a biphenyl-bridged imidazole dimer revealed bywide range transient absorption spectroscopy” Chem Commun 51: 1375-78,each of which is incorporated herein by reference in its entirety.

Similar to the conventional HABI molecules, the bridged HABI moleculesform radicals instantaneously upon exposure to UV light. However, theradicals are linked by a covalent bond (e.g., one or more covalent bondsand/or, e.g., an R group), which prevents diffusion of the radicals awayfrom one another and thus accelerates the thermally driven reformationof the bridged HABI molecule. Accordingly, the bridged HABI moleculesinstantaneously produce radicals upon UV light irradiation and theradicals rapidly disappear when UV irradiation is stopped.

As used herein, the term “bridged HABI” refers to a HABI molecule inwhich the triphenylimidazolyl radicals are linked (e.g., by one or morecovalent bonds or by an R group) to each other such that they do notdiffuse away from one another upon hemolytic cleavage of the bondconnecting the imidazole centers (e.g., by light). As used herein, theterm “X-bridged HABI”, where “X” refers to an R group (e.g., moiety,chemical group, etc.), refers to a HABI wherein the imidazolyl moietiesare linked by the R group. See, e.g., FIGS. 5A, 5B, 5C, and 5D.

In an exemplary embodiment, the half-life of the radicals formed from anaphthalene-bridged HABI and a [2.2]paracyclophane-bridged HABI dimerare approximately 830 ms and 33 ms at 25° C. in benzene, respectively.See, e.g., Iwahori et al. (2007) “Rational design of a new class ofdiffusion-inhibited HABI with fast back-reaction” J Phys Org Chem 20:857-63; Fujita et al. (2008) “Photochromism of a radicaldiffusion-inhibited hexaarylbiimidazole derivative with intensecoloration and fast decoloration performance” Org Lett 10: 3105-08;Kishimoto and Abe (2009) “A fast photochromic molecule that colors onlyunder UV light” J Am Chem Soc 131: 4227-29, each of which isincorporated herein in its entirety.

Additional exemplary embodiments relate to use of a HABI in which theimidazole moieties are linked by a 1,1′-bi-naphthol bridge. The1,1′-bi-naphthol-bridged HABI has a half-life of approximately 100 μs.See, e.g., Iwasaki et al. (2014) “A chiral BINOL-bridged imidazole dimerpossessing sub-millisecond fast photochromism” Chem Commun 50: 7481-84,incorporated herein by reference. In some embodiments, the technologyrelates to use of a HABI comprising a bond linking the imidazolyl groups(e.g., a bond links the imidazolyl groups; see, e.g., FIG. 5D) that hasa half-life of approximately 100 ns, which is the fastest thermal backreaction for a HABI compound presently known in the art. See, e.g.,Yamaguchi et al. (2015) “Nanosecond photochromic molecular switching ofa biphenyl-bridged imidazole dimer revealed by wide range transientabsorption spectroscopy” Chem Commun 51: 1375-78, incorporated herein byreference in its entirety. In some embodiments, the bridged HABIcomprises a cyclophane (see, e.g., FIG. 5E).

Accordingly, the technology relates in some embodiments to use ofbridged HABI molecules as photoactivatable inhibitors of polymerization.In some embodiments, the bridged HABI molecules form a radical uponirradiation by light (e.g., at an appropriate wavelength to form aradical from the HABI). In some embodiments, the radical rapidlydisappears upon stopping the irradiation by light. For example,embodiments relate to a bridged HABI that forms a radical having ahalf-life of approximately 100 ns to 100 μs to 100 ms to 100 s (e.g.,10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700,800, 900, or 1000 ns; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300,400, 500, 600, 700, 800, 900, or 1000 μs; 10, 20, 30, 40, 50, 60, 70,80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ms; or 0,20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800,900, or 1000 s). That is, after formation of the radical by irradiationof the bridged HABI at the appropriate wavelength, the radical rapidlyreforms the bridged HABI upon stopping the irradiation. Consequently,the radical is only formed in the region irradiated by the appropriatewavelength to form a radical from the HABI.

Accordingly, the technology provided herein relates to photoinhibitorsthat are activated by light to form a polymerization inhibiting speciesand that have a fast back reaction that reforms the inactivephotoinhibitor from the polymerization inhibiting species. When notactivated by light (e.g., in the inactive state), the photoinhibitors donot have inhibiting activity and do not have initiating activity; whenactivated by light, the photoinhibitors form an inhibiting species thatinhibits polymerization and that does not initiate polymerization.Accordingly, the technology provided herein relates to photoinhibitionthat is quickly turned “on” and quickly turned “off” by the presence andabsence of light and that does not have undesirable inhibition and/orinitiation activities.

In some embodiments, the photoinhibitor compounds of the technology(e.g., compounds having fast back reaction kinetics and/or HABI (e.g.,bridged HABI compounds)) do not exhibit photoinitiation activity whenirradiated (e.g., when photoactivated) and thus only exhibitphotoinhibition when irradiated (e.g., when photoactivated). Moreover,in some embodiments, the non-photoactivated photoinhibitor compounds ofthe technology do not retard polymerization rates (e.g., by chaintransfer reactions).

In some embodiments, the photoinhibitor compounds are precisephotoinhibitor compounds.

In some embodiments, the photoinhibitor compounds are precisephotoinhibitor compounds having fast back reaction kinetics.

Finally, in some embodiments, the photoinhibitor compounds of thetechnology typically exhibit very weak or zero absorbance in the blueregion of the electromagnetic spectrum and moderately absorb in thenear-UV region of the electromagnetic spectrum, thus complementing theabsorbance spectra of several photoinitiators activated by blue light.

Like HABI compounds, bridged HABI compounds do not exhibitphotoinitiation activity when irradiated. Moreover, bridged HABIcompounds do not participate in chain transfer reactions and thuspolymerization rates are not inherently retarded by the presence of HABIcompounds. Finally, bridged HABI compounds typically exhibit very weakabsorbance in the blue region of the electromagnetic spectrum andmoderately absorb in the near-UV region of the electromagnetic spectrum,thus complementing the absorbance spectrum of several photoinitiatorsactivated by blue light. Finally, bridged HABI compounds exhibit fastback reaction kinetics.

Compositions

The technology relates to compositions for producing a polymer, e.g., toproduce a patterned article of manufacture, e.g., for three-dimensional(3D) printing, etc. In particular, the technology relates to producing apolymer from polymerizable monomers (e.g., from a “resin”). Thetechnology is not limited in the polymerizable monomer used providedthat polymerization of the monomer is initiated by a radical formed fromthe photoinitiator and polymerization of the monomer is inhibited by aradical formed from the photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)). That is, embodiments provide that polymerization ofthe monomers occurs where the photoinitiator is activated by a firstwavelength of light and polymerization of the monomers does not occurwhere the photoinhibitor compound having fast back reaction kinetics(e.g., a HABI photoinhibitor (e.g., a bridged HABI photoinhibitor)) isactivated by a second wavelength of light.

Accordingly, embodiments relate to compositions comprising a monomer, aphotoinitiator, and a photoinhibitor (e.g., a photoinhibitor compoundhaving fast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor))). In some embodiments, compositionsfurther comprise one or more light absorbing dyes. In some embodiments,compositions further comprise one or more coinitiators. In someembodiments, compositions comprise one or more solvents.

Embodiments of compositions comprise a photoinhibitor compound havingfast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor)). See, e.g., FIGS. 5A and 5B, in which theR group is any group that covalently links the two triphenylimidazolylgroups; FIG. 5C; and FIG. 5D, in which a bond links the imidazolylgroups and each R is a substituent (e.g., in some embodiments amethoxy). See, e.g., FIG. 5C showing a bridged HABI photoinhibitor inwhich the R group is naphthalene and FIG. 5D showing a bridged HABIphotoinhibitor in which the phenyl groups are directly linked by a bond.See, e.g., FIG. 5E showing a bridged HABI photoinhibitor in which the Rgroup is a cyclophane (e.g., a cyclophane links the imidazolyl groups).

The bridged HABI photoinhibitor may be one known in the art, asdescribed herein, or a substituted variation thereof (e.g., comprisingone or more moieties (e.g., an alkyl, halogenated alkyl, alkoxyalkyl,alkylamino, cycloalkyl, heterocycloalkyl, polyalkylene, alkoxyl,alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl,aldehyde, amino, halo, or thio) on one or more phenyl rings and/or onthe R group).

In some embodiments, the technology provides a composition comprising aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)) at approximately0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12,0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24,0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60,0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5,4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

The technology relates to compositions comprising any suitablepolymerizable liquid. In some embodiments, the liquid (also referred toas “resin” herein) comprises monomers, particularly a photopolymerizableand/or free radical polymerizable monomers, and a suitable initiatorsuch as a free radical initiator, and combinations thereof. Examplesinclude, but are not limited to, acrylics, methacrylics, acrylamides,styrenics, olefins, halogenated olefins, cyclic alkenes, maleicanhydride, alkenes, alkynes, carbon monoxide, functionalized oligomers,multifunctional cute site monomers, functionalized PEGs, etc., includingcombinations thereof. In some embodiments, polymerizable monomersinclude, but are not limited to, monomeric, dendritic, and oligomericforms of acrylates, methacrylates, vinyl esters, styrenics, othervinylic species, and mixtures thereof. Examples of liquid resins,monomers, and initiators include, but are not limited to, thosedescribed in U.S. Pat. Nos. 8,232,043; 8,119,214; 7,935,476; 7,767,728;7,649,029; in Int'l Pat. Pub. No. WO 2012129968 A1; in Chinese patentapplication CN 102715751 A; and in Japanese patent application JP2012210408A, each of which is incorporated herein by reference.

In particular, embodiments provide compositions comprising a monomersuch as, e.g., hydroxyethyl methacrylate; n-lauryl acrylate;tetrahydrofurfuryl methacrylate; 2,2,2-trifluoroethyl methacrylate;isobornyl methacrylate; polypropylene glycol monomethacrylates,aliphatic urethane acrylate (e.g., RAHN GENOMER 1122); hydroxyethylacrylate; n-lauryl methacrylate; tetrahydrofurfuryl acrylate;2,2,2-trifluoroethyl acrylate; isobornyl acrylate; polypropylene glycolmonoacrylates; trimethylpropane triacrylate; trimethylpropanetrimethacrylate; pentaerythritol tetraacrylate; pentaerythritoltetraacrylate; triethyleneglycol diacrylate; triethylene glycoldimethacrylate; tetrathyleneglycol diacrylate; tetrathylene glycoldimethacrylate; neopentyldimethacrylate; neopentylacrylate; hexanedioldimethacylate; hexane diol diacrylate; polyethylene glycol 400dimethacrylate; polyethylene glycol 400 diacrylate; diethylglycoldiacrylate; diethylene glycol dimethacrylate; ethyleneglycol diacrylate;ethylene glycol dimethacrylate; ethoxylated bis phenol A dimethacrylate;ethoxylated bis phenol A diacrylate; bisphenol A glycidyl methacrylate;bisphenol A glycidyl acrylate; ditrimethylolpropane tetraacrylate; orditrimethylolpropane tetraacrylate.

Particular embodiments provide compositions comprising an acrylatemonomer, e.g., an acrylate monomer, a methacrylate monomer, etc. In someembodiments, the acrylate monomer is an acrylate monomer such as, butnot limited to, (meth)acrylic acid monomers such as (meth)acrylic acid,methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate,isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate,tert-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate,cyclohexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate,2-ethylhexyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate,dodecyl(meth)acrylate, phenyl(meth)acrylate, toluoyl(meth)acrylate,benzyl(meth)acrylate, 2-methoxyethyl(meth)acrylate,3-methoxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate,2-hydroxypropyl(meth)acrylate, stearyl(meth)acrylate,glycidyl(meth)acrylate, 2-aminoethyl(meth)acrylate,3-(methacryloyloxypropyl)trimethoxysilane, (meth)acrylic acid-ethyleneoxide adducts, trifluoromethylmethyl(meth)acrylate,2-trifluoromethylethyl(meth)acrylate,2-perfluoroethylethyl(meth)acrylate,2-perfluoroethyl-2-perfluorobutylethyl(meth)acrylate,2-perfluoroethyl(meth)acrylate, perfluoromethyl(meth)acrylate,diperfluoromethylmethyl(meth)acrylate,2-perfluoromethyl-2-perfluoroethylethyl(meth)acrylate,2-perfluorohexylethyl(meth)acrylate, 2-perfluorodecylethyl(meth)acrylateand 2-perfluorohexadecylethyl(meth)acrylate.

Some embodiments provide a composition comprising n-butyl acrylate,methyl methacrylate, 2-ethylhexyl acrylate, methyl acrylate, tert-butylacrylate, 2-hydroxyethyl acrylate, glycidyl methacrylate, or acombination thereof. However, embodiments of the technology encompasscompositions comprising any acrylate or (meth)acrylate.

In some embodiments, the technology provides a composition comprising amonomer at approximately 1 to 99.99 wt % (e.g., approximately 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.1, 99.2. 99.3,99.4, 99.5, 99.6, 99.7, 99.8, 99.9, 99.95, to 99.99 wt %).

Embodiments of the technology provide a composition comprising aphotoinitiator. The technology is not limited in the photoinitiatorprovided it is chemically compatible with the photoinhibitor compoundhaving fast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor)) described herein. Further, embodimentsrelate to use of a photoinitiator that is optically compatible with thephotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)) described herein.In particular, the technology comprises use of a photoinitiator that isactivated by a wavelength of light that is different than the wavelengthof light that activates the photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)).

Accordingly, the technology comprises use of a wide variety ofphotoinitiator compounds and irradiation conditions for activating thephotoinitiator to effect the photoinitiation process. Non-limitingexamples of the photoinitiator include benzophenones, thioxanthones,anthraquinones, camphorquinones, thioxanthones, benzoylformate esters,hydroxyacetophenones, alkylaminoacetophenones, benzil ketals,dialkoxyacetophenones, benzoin ethers, phosphine oxides, acyloximinoesters, alphahaloacetophenones, trichloromethyl-S-triazines,titanocenes, dibenzylidene ketones, ketocoumarins, dye sensitizedphotoinitiation systems, maleimides, and mixtures thereof. Particularexamples of photoinitiators include, e.g.,1-hydroxy-cyclohexyl-phenyl-ketone (IRGACURE 184; BASF, Hawthorne,N.J.); a 1:1 mixture of 1-hydroxy-cyclohexyl-phenyl-ketone andbenzophenone (IRGACURE 500; BASF);2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR 1173; BASF);2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (IRGACURE2959; BASF); methyl benzoylformate (DAROCUR MBF; BASF);oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester;oxy-phenyl-acetic 2-[2-hydroxy-ethoxy]-ethyl ester; a mixture ofoxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester andoxy-phenyl-acetic 2-[2-hydroxy-ethoxy]-ethyl ester (IRGACURE 754; BASF);alpha,alpha-dimethoxy-alpha-phenylacetophenone (IRGACURE 651; BASF);2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)-phenyl]-1-butanone(IRGACURE 369; BASF);2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone(IRGACURE 907; BASF); a 3:7 mixture of2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl) phenyl]-1-butanone andalpha,alpha-dimethoxy-alpha-phenylacetophenone per weight (IRGACURE1300; BASF); diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide (DAROCURTPO; BASF); a 1:1 mixture of diphenyl-(2,4,6-trimethylbenzoyl)-phosphineoxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR 4265; BASF);phenyl bis(2,4,6-trimethyl benzoyl) phosphine oxide, which may be usedin pure form (IRGACURE 819; BASF, Hawthorne, N.J.) or dispersed in water(45% active, IRGACURE 819DW; BASF); 2:8 mixture of phosphine oxide,phenyl bis(2,4,6-trimethyl benzoyl) and2-hydroxy-2-methyl-1-phenyl-1-propanone (IRGACURE 2022; BASF); IRGACURE2100, which comprises phenyl-bis(2,4,6-trimethylbenzoyl)-phosphineoxide); bis-(eta5-2,4-cyclopentadien-1-yl)-bis-[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]-titanium (IRGACURE 784; BASF); (4-methylphenyl)[4-(2-methylpropyl)phenyl]-iodonium hexafluorophosphate (IRGACURE 250;BASF);2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-butan-1-one(IRGACURE 379; BASF);4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone (IRGACURE 2959;BASF); bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide;a mixture of bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphineoxide and 2-hydroxy-2-methyl-1-phenyl-propanone (IRGACURE 1700; BASF);4-Isopropyl-9-thioxanthenone; and mixtures thereof.

In some embodiments, the photoinitiator is used in an amount rangingfrom approximately 0.01 to approximately 25 weight percent (wt %) of thecomposition (e.g., from approximately 0.1 to approximately 3.0 wt % ofthe composition (e.g., approximately 0.2 to 0.5 wt % of thecomposition)). In some embodiments, the technology provides acomposition comprising a photoinitiator at approximately 0.01, 0.02,0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14,0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26,0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70,0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5,5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

Embodiments of the technology provide a composition further comprising acoinitiator, e.g., to enhance the polymerization rate, extent, quality,etc. The technology is not limited in the coinitiator. Non-limitingexamples of co-initiators include primary, secondary, and tertiaryamines; alcohols; and thiols. Particular examples of coinitiatorsinclude, e.g., dimethylaminobenzoate, isoamyl 4-(dimethylamino)benzoate,2-ethylhexyl 4-(dimethylamino)benzoate; ethyl 4-(dimethylamino)benzoate;3-(dimethylamino)propyl acrylate; 2-(dimethylamino)ethyl methacrylate;4-(dimethylamino)benzophenones, 4-(diethylamino)benzophenones;4,4′-bis(diethylamino)benzophenones; methyl diethanolamine;triethylamine; hexane thiol; heptane thiol; octane thiol; nonane thiol;decane thiol; undecane thiol; dodecane thiol; isooctyl3-mercaptopropionate; pentaerythritol tetrakis(3-mercaptopropionate);4,4′-thiobisbenzenethiol; trimethylolpropane tris(3-mercaptopropionate);CN374 (SARTOMER); CN371 (SARTOMER), CN373 (SARTOMER), GENOMER 5142(RAHN); GENOMER 5161 (RAHN); GENOMER 5271 (RAHN); GENOMER 5275 (RAHN),and TEMPIC (BRUNO BOC, Germany).

In some embodiments, the coinitiator is used in an amount ranging fromapproximately 0.0 to approximately 25 weight percent (wt %) of thecomposition (e.g., approximately 0.1 to approximately 3.0 wt % of thecomposition (e.g., 0.1 to 1.0 wt %) when used in embodiments of thecompositions). In some embodiments, the technology provides acomposition comprising a coinitiator at approximately 0, 0.01, 0.02,0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14,0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26,0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70,0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5,5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

Some embodiments comprise use of a photon absorbing component, e.g., alight blocking dye. In some embodiments, a photon absorbing component isselected in accordance with the wavelengths of the first and secondlights. In some embodiments, dyes are used to both attenuate light andto transfer energy to photoactive species increasing the sensitivity ofthe system to a given wavelength for either or both photoinitiation andphotoinhibition processes. In some embodiments, the concentration of thechosen dye is highly dependent on the light absorption properties of thegiven dye and ranges from approximately 0.001 to approximately 5 weightpercent (wt %) of the composition. Useful classes of dyes includecompounds commonly used as UV absorbers for decreasing weathering ofcoatings including, such as, 2-hydroxyphenyl-benzophenones;2-(2-hydroxyphenyl)-benzotriazoles; and 2-hydroxyphenyl-s-triazines.Other useful dyes include those used for histological staining or dyingof fabrics. A non-limiting list includes Martius yellow, Quinolineyellow, Sudan red, Sudan I, Sudan IV, eosin, eosin Y, neutral red, andacid red. Pigments can also be used to scatter and attenuate light.

In some embodiments, the photon absorbing component (e.g., a lightblocking dye) is used in an amount ranging from approximately 0.0 toapproximately 25 weight percent (wt %) of the composition (e.g.,approximately 0.1 to approximately 3.0 wt % of the composition (e.g.,0.1 to 1.0 wt %) when used in embodiments of the compositions). In someembodiments, the technology provides a composition comprising a photonabsorbing component (e.g., a light blocking dye) at approximately 0,0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12,0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24,0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60,0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5,4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

Some embodiments do not comprise a photon absorbing component (e.g., insome embodiments, compositions are “photoabsorber-free”). In particular,embodiments are provided in which compositions are photoabsorber-free toincrease or maximize the penetration of a wavelength of light through acomposition as described herein (e.g., comprising a polymerizablemonomer, a photoinitiator, and a photoinhibitor compound having fastback reaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridgedHABI photoinhibitor))).

In some embodiments, a composition further comprises solid particlessuspended or dispersed therein. Any suitable solid particle can be used,depending upon the end product being fabricated. In some embodiments,the solid particles are metallic, organic/polymeric, inorganic, orcomposites or mixtures thereof. In some embodiments, the solid particlesare nonconductive, semi-conductive, or conductive (including metallicand non-metallic or polymer conductors); in some embodiments, the solidparticles are magnetic, ferromagnetic, paramagnetic, or nonmagnetic. Theparticles can be of any suitable shape, including spherical, elliptical,cylindrical, etc.

In some embodiments, a composition comprises a pigment, dye, activecompound, pharmaceutical compound, or detectable compound (e.g.,fluorescent, phosphorescent, radioactive). In some embodiments, acomposition comprises a protein, peptide, nucleic acid (DNA, RNA (e.g.,siRNA)), sugar, small organic compound (e.g., drug and drug-likecompound), etc., including combinations thereof.

In some embodiments, the compositions are homogenous. The technology isrelated to forming polymerized structures; accordingly, in someembodiments, the compositions are heterogeneous because thecompositions, in some embodiments, comprise polymerized andnon-polymerized regions. In some embodiments, compositions of thetechnology comprise a polymer (e.g., comprising polymerized monomers).In some embodiments, a polymerized region is patterned, localized, etc.

Methods

The technology relates to producing a polymer, e.g., bythree-dimensional printing, stereolithography, photofabrication, etc. Insome embodiments, methods comprise providing a composition comprising apolymerizable monomer, a photoinitiator, and a photoinhibitor compoundhaving fast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor)).

In some embodiments, methods comprise a step of irradiating thecomposition with a first wavelength of light, e.g., to initiatepolymerization of monomers by producing a radical from thephotoinitiator. In some embodiments, methods comprise a step ofirradiating the composition with a second wavelength of light, e.g., tostop polymerization of monomers by producing a radical from thephotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)). Thus, in someembodiments, a first wavelength of light is focused on a composition asprovided herein, e.g., to polymerize a polymerizable monomer in thecomposition (“photoinitiation”). In some embodiments, a second,different wavelength of light is focused on a composition as providedherein, e.g., to slow, hinder, and/or stop the polymerization of thepolymerizable monomer (“photoinhibition”).

In some embodiments, the first wavelength is produced by a first lightsource, and the second wavelength is produced by a second light source.In some embodiments, the first wavelength and the second wavelength areproduced by the same light source. In some embodiments, the firstwavelength and second wavelength have emission peak wavelengths that areat least 5 or 10 nm apart from one another (e.g., the emission peak ofthe first wavelength is at least 5, 6, 7, 8, 9, 10, or more nm apartfrom the emission peak of the second wavelength).

In particular, as discussed herein, the technology relates to use of afirst wavelength to activate a photoinitiator. Activating thephotoinitiator produces an initiating moiety (e.g., initiating radicals)from the photoinitiator. The initiating radicals initiate polymerizationof the polymerizable monomers. Further, as discussed herein, thetechnology relates to use of a second wavelength to activate aphotoinhibitor. Activating the photoinhibitor produces an inhibitingmoiety (e.g., inhibiting radicals) from the photoinhibitor. Theinhibiting radicals prevent polymerization of the polymerizablemonomers. Accordingly, embodiments of the technology relate to use of 1)a first wavelength of light that activates the photoinitiator and thatdoes not activate the photoinhibitor; and 2) a second wavelength oflight that activates the photoinhibitor and that does not activate thephotoinhibitor. Thus, the photoinhibitor, photoinitiator, firstwavelength, and second wavelength are chosen such that: 1) the firstwavelength of light activates the photoinitiator and does not activatethe photoinhibitor; and 2) the second wavelength of light activates thephotoinhibitor and does not activate the photoinhibitor.

In some embodiments, the first wavelength is at or near the peak of theabsorbance spectrum of the photoinitiator, e.g., within 50 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) of thepeak of the absorbance spectrum of the photoinitiator. In someembodiments, the second wavelength is at or near the peak of theabsorbance spectrum of the photoinhibitor, e.g., within 50 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) of thepeak of the absorbance spectrum of the photoinhibitor.

A wavelength of light that is not strongly absorbed penetrates moredeeply into a composition comprising an absorbing compound (e.g., aphotoinitiator or photoinhibitor) and therefore activates a largervolume of photoactivated compound (e.g., a photoinitiator orphotoinhibitor). Accordingly, in some embodiments, the first wavelengthis chosen to be a wavelength that activates the photoinitiator, but thatis also not strongly absorbed by the photoinitiator; similarly, in someembodiments, the second wavelength is chosen to be a wavelength thatactivates the photoinhibitor, but that is also not strongly absorbed bythe photoinhibitor.

In some embodiments, the first wavelength is not near the peak of theabsorbance spectrum of the photoinitiator, e.g., at least 50 nm (e.g.,at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) away fromthe peak of the absorbance spectrum of the photoinitiator. In someembodiments, the second wavelength is not near the peak of theabsorbance spectrum of the photoinhibitor, e.g., at least 50 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) away fromthe peak of the absorbance spectrum of the photoinhibitor. Similarly, insome embodiments, the absorbance of the photoinitiator at the firstwavelength is less than 25% (e.g., less than 25, 24, 23, 22, 21, 20, 19,18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4.5, 4, 3.5, 3, 2.5,2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6,0.5, 0.4, 0.3, 0.2, 0.1, or 0.05%) of the absorbance of thephotoinitiator at the wavelength of the absorbance peak of thephotoinitiator. And, in some embodiments, the absorbance of thephotoinhibitor at the second wavelength is less than 25% (e.g., lessthan 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9,8, 7, 6, 5, 4.5, 4, 3.5, 3, 2.5, 2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3,1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, or 0.05%) ofthe absorbance of the photoinhibitor at the wavelength of the absorbancepeak of the photoinhibitor.

In some embodiments, a first light source initiates polymerization ofmonomers in a polymerizable composition. Further, a second light sourceproviding a different wavelength of light is provided to inhibit (e.g.,prevent) and spatially restrict polymerization of monomers in thepolymerizable composition. In some embodiments, the first and secondlight sources irradiate overlapping regions of the composition. In someembodiments, the first and second light sources irradiate adjacentregions of the composition. In some embodiments, the first and secondlight sources irradiate different regions of the composition.

In some embodiments, light is provided in a pattern. In someembodiments, the first wavelength of light is provided as a pattern. Insome embodiments, the second wavelength of light is provided as apattern. The first and second wavelengths may be provided in patternsthat are the same or different. In some embodiments, the methodscomprise irradiating a composition as described herein with a pattern ofa first wavelength of light. In some embodiments, the methods compriseirradiating a composition as described herein with a pattern of a secondwavelength of light. In some embodiments, different patterns of lightfor two different wavelengths of light are used. In some embodiments,the patterns overlap in different configurations. In some embodiments,the methods comprise irradiating a composition as described herein witha first pattern of a first wavelength of light. In some embodiments, themethods comprise irradiating a composition as described herein with asecond pattern of a second wavelength of light.

In some embodiments, the shape and/or size of a polymerized region isdetermined by the difference of the photoinitiating pattern of the firstlight source and the photoinhibiting pattern of the second light source.

In some embodiments, methods comprise irradiating a composition providedherein with a light of a first wavelength and a light of a secondwavelength. In some embodiments, the methods comprise moving a firstwavelength of light and a second wavelength of light to move the regionof the composition irradiated by the first wavelength, secondwavelength, and/or both the first and second wavelengths, e.g., as afunction of time. Accordingly, irradiating the composition with thefirst and second wavelengths produces arbitrary three-dimensionalobjects comprising polymer.

In some embodiments, photoinhibition of polymerization is rapidlyeliminated in the absence of the photoinhibition irradiation wavelengthbecause the photoinhibitor compound having fast back reaction kinetics(e.g., a HABI photoinhibitor (e.g., a bridged HABI photoinhibitor))reforms from the inhibiting radical with a half-life of approximately100 ns to 100 μs to 100 ms to 100 s (e.g., 10, 20, 30, 40, 50, 60, 70,80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ns; 10, 20,30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900,or 1000 μs; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500,600, 700, 800, 900, or 1000 ms; or 0, 20, 30, 40, 50, 60, 70, 80, 90,100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 s).

In particular, while the bridged HABI radicals are incapable ofinitiating free radical polymerization of polymerizable monomers (e.g.,methacrylate monomers), the bridged HABI radicals rapidly recombine withand terminate the growing polymer chain.

In some embodiments, the methods further comprise varying the intensityof the first wavelength of light. In some embodiments, the methodsfurther comprise varying the intensity of the second wavelength oflight. In some embodiments, varying the intensity of the first and/orsecond wavelength of light changes the region of the composition inwhich polymerization occurs.

In some embodiments, the methods comprise varying the intensity and/orthe wavelength of the first source of light. In some embodiments, themethods further comprise varying the intensity and/or wavelength of thesecond source of light. In some embodiments, varying the intensityand/or wavelength of the first and/or second sources of light changesthe region of the composition in which polymerization occurs.

In some embodiments, methods comprise a step of irradiating thecomposition with a first source of light, e.g., to initiatepolymerization of monomers by producing a radical from thephotoinitiator. In some embodiments, methods comprise a step ofirradiating the composition with a second source of light, e.g., to stoppolymerization of monomers by producing a radical from thephotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)). In someembodiments, methods comprise a step of irradiating the composition witha first source of light, e.g., to produce a region (e.g., athree-dimensional region) within the composition where monomerspolymerize. In some embodiments, methods comprise a step of irradiatingthe composition with a second source of light, e.g., to produce a region(e.g., a three-dimensional region) within the composition where monomersdo not polymerize. In some embodiments, a region irradiated by both thefirst source of light and the second source of light is a region withinthe composition where monomers do not polymerize because the initiatingradicals do not initiate polymerization in the presence of theinhibiting radicals.

In some embodiments, methods comprise producing a polymerizing region ina composition comprising a polymerizable monomer, a photoinitiator, anda photoinhibitor compound having fast back reaction kinetics (e.g., aHABI photoinhibitor (e.g., a bridged HABI photoinhibitor)). In someembodiments, the polymerizing region is a three-dimensional spacecontacted by light having a wavelength and intensity that activates thephotoinitiator; in some embodiments, the polymerizing region is notcontacted by light having an intensity and/or wavelength that activatesthe photoinhibitor. That is, in some embodiments the polymerizing regioncomprises sufficient photoinitiating radicals to produce polymer frommonomer but does not comprise sufficient photoinhibitor to inhibitproduction of polymer from monomer.

As described herein, the size, wavelength, intensity, and pattern of thefirst and second wavelengths of light produce the three-dimensionalspace in the composition that is the polymerizing region. In someembodiments, the three-dimensional space has dimensions of approximately0.5 μm-100 cm×0.5 μm-100 cm×0.5 μm-100 cm. Accordingly, thethree-dimensional space is shaped, in various embodiments, as a dot, athin rod or line, a slab, a prism, or a cube. The shape of thepolymerizing region, however, is not limited to these particularlylisted shapes and can be any arbitrary shape produced by theintersecting patterns of the first and second wavelengths of light.

Systems

In some embodiments, the technology relates to systems, e.g., comprisinga composition as described herein and one or more light sources.

System embodiments comprise a suitable light source (or combination oflight sources) selected to be appropriate for the particular monomer(“resin”), photoinitiator, and/or photoinhibitor employed (e.g., aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor))). Whileembodiments are discussed in terms of a light source, embodiments alsoinclude sources of radiation including an electron beam and otherionizing radiation sources.

In some embodiments, the light source is an actinic radiation source(e.g., one or more light sources providing visible and/or ultravioletelectromagnetic radiation). In some embodiments, a light source is,e.g., an incandescent light, fluorescent light, phosphorescent orluminescent light, laser, light-emitting diode, etc., including arraysthereof. In some embodiments, a light source provides even coverage oflight. Accordingly, in some embodiments a light source is a collimatedbeam or a planar waveguide, e.g., to provide even coverage of a light.

In some embodiments, light is provided in a pattern. Accordingly, insome embodiments a light source is a liquid crystal display (LCD), lightemitting diode (LED), or a digital light projector (DLP), e.g., todeliver a pattern of light. In some embodiments, the light sourceincludes a pattern-forming element operatively associated with acontroller. In some embodiments, the light source or pattern formingelement comprises a digital (or deformable) micromirror device (DMD)with digital light processing (DLP), a spatial modulator (SLM), or amicroelectromechanical system (MEMS) mirror array, a mask (aka areticle), a silhouette, or a combination thereof. See, U.S. Pat. No.7,902,526, incorporated herein by reference. In some embodiments, thelight source comprises a spatial light modulation array such as a liquidcrystal light valve array or micromirror array or DMD (e.g., with anoperatively associated digital light processor, typically in turn underthe control of a suitable controller), configured to carry out exposureor irradiation of a composition as described herein (e.g., by masklessphotolithography). See, e.g., U.S. Pat. Nos. 6,312,134; 6,248,509;6,238,852; and 5,691,541, incorporated herein by reference.

In some embodiments, the light source(s) direct a first light and asecond light into a composition as described herein. The second lighthas a second wavelength selected to produce photoinhibition (e.g., toproduce a photoinhibition layer and/or to produce a photoinhibitionvolume) within the liquid. The first light has a first wavelength,different than the second wavelength, that is used to polymerize thephotoactive resin in the liquid (e.g., within a photoinitiation layer).In some embodiments, the first light has a first wavelength thatproduces an initiating radical from the photoinitiator and the secondlight has a second wavelength, different than the first wavelength, thatforms a radical from a photoinhibitor compound having fast back reactionkinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)). In some embodiments, the first and/or second light(s)are provided in accordance with a defined pattern or patterns. Inaddition, the one or more light sources can be a dual wavelengthillumination source device or separate illumination devices.

In some embodiments, the one or more light sources is/are connected witha computer (or other controller). In some embodiments, the technologycomprises use of a computer and/or microprocessor. For example,embodiments of technology are implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, includingembodiments of methods described herein. For example, embodiments of thetechnology are implemented using one or more modules of computer programinstructions encoded on a computer-readable medium for execution by, orto control the operation of, data processing apparatus. Thecomputer-readable medium can be a manufactured product, such as harddrive in a computer system or an optical disc sold through retailchannels, or an embedded system. The computer-readable medium can beacquired separately and later encoded with the one or more modules ofcomputer program instructions, such as by delivery of the one or moremodules of computer program instructions over a wired or wirelessnetwork. The computer-readable medium can be a machine-readable storagedevice, a machine-readable storage substrate, a memory device, or acombination of one or more of them.

In some embodiments, the technology comprises use of a “data processingapparatus”. The term “data processing apparatus” encompasses allapparatus, devices, and machines for processing data, including by wayof example a programmable processor, a computer, or multiple processorsor computers. The apparatus can include, in addition to hardware, codethat creates an execution environment for the computer program inquestion, e.g., code that constitutes processor firmware, a protocolstack, a database management system, an operating system, a runtimeenvironment, or a combination of one or more of them. In addition, theapparatus can employ various different computing model infrastructures,such as web services, distributed computing and grid computinginfrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A computer program does notnecessarily correspond to a file in a file system. A program can bestored in a portion of a file that holds other programs or data (e.g.,one or more scripts stored in a markup language document), in a singlefile dedicated to the program in question, or in multiple coordinatedfiles (e.g., files that store one or more modules, sub-programs, orportions of code). A computer program can be deployed to be executed onone computer or on multiple computers that are located at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

The processes and logic flows described herein can be performed by,and/or under the control of, one or more programmable processorsexecuting one or more computer programs to perform functions byoperating on input data and generating output. The processes and logicflows can also be performed by, and apparatus can also be implementedas, special purpose logic circuitry, e.g., an FPGA (field programmablegate array) or an ASIC (application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto-optical disks, or optical disks. However, a computerneed not have such devices. Moreover, a computer can be embedded inanother device, e.g., a mobile telephone, a personal digital assistant(PDA), a mobile audio or video player, a game console, a GlobalPositioning System (GPS) receiver, or a portable storage device (e.g., auniversal serial bus (USB) flash drive), etc. Devices suitable forstoring computer program instructions and data include all forms ofnon-volatile memory, media and memory devices, including by way ofexample semiconductor memory devices, e.g., EPROM, EEPROM, and flashmemory devices; magnetic disks, e.g., internal hard disks or removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,special purpose logic circuitry.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input.

Some embodiments of the technology are implemented in a computing systemthat includes a back-end component, e.g., as a data server, or thatincludes a middleware component, e.g., an application server, or thatincludes a front-end component, e.g., a client computer having agraphical user interface or a web browser through which a user caninteract with an implementation of the subject matter described is thisspecification, or any combination of one or more such back-end,middleware, or front-end components. The components of the system can beinterconnected by any form or medium of digital data communication,e.g., a communication network. Examples of communication networksinclude a local area network (“LAN”) and a wide area network (“WAN”), aninter-network (e.g., the Internet), and peer-to-peer networks (e.g., adhoc peer-to-peer networks).

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

A computer includes a processor and a memory. The processor can be oneor more hardware processors, which can each include multiple processorcores. The memory can include both volatile and non-volatile memory,such as Random Access Memory (RAM) and Flash RAM. The computer caninclude various types of computer storage media and devices, which caninclude the memory, to store instructions of programs that run on theprocessor. For example, a 3D printing program can be stored in thememory and run on the processor to implement the techniques describedherein.

Kits

Some embodiments relate to kits. Embodiments of kits comprise one ormore compositions, or separately packaged components of compositions, asdescribed herein. For example, in some embodiments, the technologyprovides kits comprising a photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)). In some embodiments, kits comprise a photoinhibitorcompound having fast back reaction kinetics (e.g., a HABI photoinhibitor(e.g., a bridged HABI photoinhibitor)), a photoinitiator, and apolymerizable monomer. In some embodiments, kits further comprise afirst and/or a second light source. Some embodiments of kits comprise areadable medium on which is provided computer instructions for producingan item from a polymerizable monomer.

Uses

The technology is not limited in its use and finds use in a wide varietyof polymer-associated technologies. In some embodiments, thecompositions, methods, and systems described herein are particularlyuseful for making three-dimensional articles. For instance, thetechnology described herein (e.g., photoinhibitor compounds having fastback reaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridgedHABI photoinhibitor))) find use in three-dimensional printing (e.g.,ultra-rapid 3D printing). Three dimensional (3D) printing or additivemanufacturing is a process in which a 3D digital model is manufacturedby the accretion of construction material. In some embodiments, a 3Dprinted object is created by utilizing computer-aided design (CAD) dataof an object through sequential construction of two dimensional (2D)layers or slices that correspond to cross-sections of 3D objects.

In some embodiments, the technology finds use in continuous layerinterface production (CLIP). In particular, in some embodiments, thephotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)) finds use inproducing a dead zone in CLIP. See, e.g., U.S. Pat. Nos. 9,205,601;9,216,546; and U.S. Pat. App. Pub. No. 2016/0067921, each of which isincorporated herein by reference. In particular, the photoinhibitorcompounds having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)) andphotoinitiator/photoinhibitor technology provided herein finds use inthe three-dimensional printing technology described in U.S. Pat. App.Pub. No. 2016/0067921 with the TED being replaced by the bridged HABIphotoinhibitors described herein.

In some embodiments, the technology finds use in stereolithography (SL).SL is one type of additive manufacturing where a liquid resin ishardened by selective exposure to a radiation to form each 2D layer. Insome embodiments, the radiation is in the form of electromagnetic waves(e.g., light, photons) or an electron beam. The most commonly appliedenergy source is ultraviolet, visible, or infrared radiation. The liquidphotopolymer resin can contain monomers, oligomers, fillers andadditives such as photoinitiators, blockers, colorants and other typesdepending on the targeted properties of the resin.

In some embodiments, the technology finds use in true additivemanufacturing and/or in direct write lithography. Products that may beproduced by the compositions, methods, and systems described hereininclude, but are not limited to, large-scale models or prototypes, smallcustom products, miniature or microminiature products or devices, etc.Examples include, but are not limited to, mechanical parts, medicaldevices and implantable medical devices such as stents, drug deliverydepots, functional structures, microneedle arrays, fibers and rods suchas waveguides, micromechanical devices, microfluidic devices, etc.

In some embodiments, the technology finds use in producing furtherexemplary products including, but not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,catheters, breast implants, testicle implants, pectoral implants, eyeimplants, contact lenses, dental aligners, microfluidics, seals,shrouds, and other applications requiring high biocompatibility;functional structures; microneedle arrays; fibers; rods; waveguides;micromechanical devices; microfluidic devices; fasteners; electronicdevice housings; gears, propellers, and impellers; wheels; mechanicaldevice housings; tools; structural elements; hinges including livinghinges; boat and watercraft hulls and decks; wheels; bottles, jars, andother containers; pipes, liquid tubes, and connectors; foot-ware soles,heels, innersoles, and midsoles; bushings, w-rings, and gaskets; shockabsorbers, funnel/hose assembly, and cushions; electronic devicehousings; shin guards, athletic cups, knee pads, elbow pads, foamliners, padding or inserts, helmets, helmet straps, head gear, shoecleats, gloves, and other wearable or athletic equipment; brushes,combs, rings, jewelry, buttons, snaps, fasteners, watch bands, or watchhousings; mobile phone or tablet casings or housings; computerkeyboards, keyboard buttons, or components; remote control buttons orcomponents; auto dashboard components, buttons, or dials; auto bodyparts, paneling, and other automotive, aircraft or boat parts; cookware,bakeware, kitchen utensils, and steamers; and any number of otherthree-dimensional objects.

Compositions for Three-Dimensional Printing

The technology relates to compositions for producing a polymer, e.g., toproduce a patterned article of manufacture, e.g., for three-dimensional(3D) printing, etc. In particular, the technology relates to producing apolymer from polymerizable monomers (e.g., from a “resin”). Thetechnology is not limited in the polymerizable monomer used providedthat polymerization of the monomer is initiated by a radical formed fromthe photoinitiator and polymerization of the monomer is inhibited by aradical formed from the photoinhibitor (e.g., a photoinhibitor compoundhaving fast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor))). That is, embodiments provide thatpolymerization of the monomers occurs where the photoinitiator isactivated by a first wavelength of light and polymerization of themonomers does not occur where the photoinhibitor (e.g., a photoinhibitorcompound having fast back reaction kinetics (e.g., a HABI photoinhibitor(e.g., a bridged HABI photoinhibitor))) is activated by a secondwavelength of light. Technologies (e.g., methods, systems, kits,apparatuses, uses, and compositions) related to use of photoinhibitors,e.g., “precise photoinhibitors”, photoinhibitors having fast backreaction kinetics, and/or “precise photoinhibitors” having fast backreaction kinetics are described in herein and in U.S. Prov. Pat. App.Ser. No. 62/632,834, which is expressly incorporated herein by referencein its entirety.

Accordingly, embodiments relate to compositions comprising a monomer, aphotoinitiator, and a photoinhibitor (e.g., a photoinhibitor compoundhaving fast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor))). In some embodiments, compositionsfurther comprise one or more light absorbing dyes. In some embodiments,compositions further comprise one or more coinitiators. In someembodiments, compositions comprise one or more solvents.

Embodiments of compositions comprise a photoinhibitor. For example, insome embodiments, the technology relates to a composition comprising aphotoinhibitor that is, e.g., a liquid or a gas. In some embodiments,the specific inhibitor depends upon the monomer being polymerized andthe polymerization reaction.

A wide variety of radicals is known which tend to preferentiallyterminate growing polymer radicals, rather than initiatingpolymerizations. For example, ketyl radicals are known in the art toterminate rather than initiate photopolymerizations. Similarly, thetechnology comprises use of a controlled radical polymerization thatuses a radical species to selectively terminate growing radical chains.Examples of terminating radicals that find use in embodiments of thetechnology include, but are not limited to, the sulfanylthiocarbonyl andother radicals generated in photoiniferter polymerizations; thesulfanylthiocarbonyl radicals used in reversible addition-fragmentationchain transfer polymerization; and the nitrosyl radicals used innitroxide mediate polymerization.

In some other embodiments, the technology comprises use of a non-radicalspecies that is generated to terminate growing radical chains, e.g., ametal/ligand complex such as those used as deactivators in atom-transferradical polymerization (ATRP). Therefore, additional non-limitingexamples of a photoinhibitor that finds use in embodiments of thetechnology include thiocarbamates, xanthates, dithiobenzoates,photoinititators that generate ketyl and other radicals that tend toterminate growing polymer chains radicals (e.g., camphorquinone andbenzophenones), ATRP deactivators, and polymeric versions thereof.

In some embodiments, the photoinhibitor is, but not limited to: zincdimethyl dithiocarbamate; zinc diethyl dithiocarbamate; zinc dibutyldithiocarbamate; nickel dibutyl dithiocarbamate; zinc dibenzyldithiocarbamate; tetramethylthiuram disulfide; tetraethylthiuramdisulfide; tetramethylthiuram monosulfide; tetrabenzylthiuram disulfide;tetraisobutylthiuram disulfide; dipentamethylene thiuram hexasulfide;N,N′-dimethyl N,N′-di(4-pyridinyl)thiuram disulfide; 3-Butenyl2-(dodecylthiocarbonothioylthio)-2-methylpropionate;4-Cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid;4-Cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanol; Cyanomethyldodecyl trithiocarbonate; Cyanomethyl[3-(trimethoxysilyl)propyl]trithiocarbonate; 2-Cyano-2-propyl dodecyltrithiocarbonate; S,S-Dibenzyl trithiocarbonate;2-(Dodecylthiocarbonothioylthio)-2-methylpropionic acid;2-(Dodecylthiocarbonothioylthio)-2-methylpropionic acidN-hydroxysuccinimide; Benzyl 1H-pyrrole-1-carbodithioate; Cyanomethyldiphenylcarbamodithioate; Cyanomethyl methyl(phenyl)carbamodithioate;Cyanomethyl methyl(4-pyridyl)carbamodithioate; 2-Cyanopropan-2-ylN-methyl-N-(pyridin-4-yl)carbamodithioate; Methyl2-[methyl(4-pyridinyl)carbamothioylthio]propionate;1-Succinimidyl-4-cyano-4-[N-methyl-N-(4-pyridyl)carbamothioylthio]pentano-ate;Benzyl benzodithioate; Cyanomethyl benzodithioate;4-Cyano-4-(phenylcarbonothioylthio)pentanoic acid;4-Cyano-4-(phenylcarbonothioylthio)pentanoic acid N-succinimidyl ester;2-Cyano-2-propyl benzodithioate; 2-Cyano-2-propyl 4-cyanobenzodithioate;Ethyl 2-(4-methoxyphenylcarbonothioylthio)acetate; 2-Phenyl-2-propylbenzodithioate; Cyanomethyl methyl(4-pyridyl)carbamodithioate;2-Cyanopropan-2-yl N-methyl-N-(pyridin-4-yl)carbamodithioate; or Methyl2-[methyl(4-pyridinyl)carbamothioylthio]propionate.

In some embodiments, the photoinhibitor is used in amounts ranging fromabout 0.01 to about 25 weight percent (wt %) of the composition. In someembodiments, the technology provides a composition comprising aphotoinhibitor at approximately 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18,0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30,0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90,0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0,7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, or 25 wt %.

Embodiments of compositions comprise a photoinhibitor (e.g., aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor))). The bridged HABIphotoinhibitor may be one known in the art, as described herein, or asubstituted variation thereof (e.g., comprising one or more moieties(e.g., an alkyl, halogenated alkyl, alkoxyalkyl, alkylamino, cycloalkyl,heterocycloalkyl, polyalkylene, alkoxyl, alkenyl, cycloalkenyl, alkynyl,cycloalkynyl, aryl, heteroaryl, aldehyde, amino, halo, or thio) on oneor more phenyl rings and/or on the R group).

In some embodiments, the photoinhibitor is a HABI compound or a bridgedHABI compound, e.g., as described herein.

In some embodiments, the technology comprises use of a photoinhibitor,e.g., a “precise photoinhibitor”, a photoinhibitor having fast backreaction kinetics, and/or a “precise photoinhibitor” having fast backreaction kinetics as described herein and in U.S. Prov. Pat. App. Ser.No. 62/632,834, which is expressly incorporated herein by reference inits entirety.

Accordingly, in some embodiments, the technology provided herein relatesto photoinhibitors that are activated by light to form a polymerizationinhibiting species and that have a fast back reaction that reforms theinactive photoinhibitor from the polymerization inhibiting species. Insome embodiments, when not activated by light (e.g., in the inactivestate), the photoinhibitors do not inhibit and/or retard polymerizationactivity and do not have initiating activity; when activated by light,the photoinhibitors form an inhibiting species that inhibitspolymerization and that does not initiate polymerization. Accordingly,the technology provided herein relates to photoinhibition that isquickly turned “on” and quickly turned “off” by the presence and absenceof light and that does not have undesirable inhibition and/or initiationactivities.

In some embodiments, the photoinhibitor compounds of the technology(e.g., compounds having fast back reaction kinetics and/or HABI (e.g.,bridged HABI compounds)) do not exhibit photoinitiation activity whenirradiated (e.g., when photoactivated) and thus only exhibitphotoinhibition when irradiated (e.g., when photoactivated). Moreover,in some embodiments, the non-photoactivated photoinhibitor compounds ofthe technology do not retard polymerization rates (e.g., by chaintransfer reactions).

In some embodiments, the photoinhibitor compounds are precisephotoinhibitor compounds.

In some embodiments, the photoinhibitor compounds are precisephotoinhibitor compounds having fast back reaction kinetics.

Finally, in some embodiments, the photoinhibitor compounds of thetechnology typically exhibit very weak or zero absorbance in the blueregion of the electromagnetic spectrum and moderately absorb in thenear-UV region of the electromagnetic spectrum, thus complementing theabsorbance spectra of several photoinitiators activated by blue light.

In some embodiments, the technology provides a composition comprising aphotoinhibitor (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)) at approximately 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18,0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30,0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90,0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0,7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, or 25 wt %.

The technology relates to compositions comprising any suitablepolymerizable liquid. In some embodiments, the liquid (also referred toas “resin” herein) comprises monomers, particularly a photopolymerizableand/or free radical polymerizable monomers, and a suitable initiatorsuch as a free radical initiator, and combinations thereof. Examplesinclude, but are not limited to, acrylics, methacrylics, acrylamides,styrenics, olefins, halogenated olefins, cyclic alkenes, maleicanhydride, alkenes, alkynes, carbon monoxide, functionalized oligomers,multifunctional cute site monomers, functionalized PEGs, etc., includingcombinations thereof. In some embodiments, polymerizable monomersinclude, but are not limited to, monomeric, dendritic, and oligomericforms of acrylates, methacrylates, vinyl esters, styrenics, othervinylic species, and mixtures thereof. Examples of liquid resins,monomers, and initiators include, but are not limited to, thosedescribed in U.S. Pat. Nos. 8,232,043; 8,119,214; 7,935,476; 7,767,728;7,649,029; in Int'l Pat. Pub. No. WO 2012129968 A1; in Chinese patentapplication CN 102715751 A; and in Japanese patent application JP2012210408A, each of which is incorporated herein by reference.

In particular, embodiments provide compositions comprising a monomersuch as, e.g., hydroxyethyl methacrylate; n-lauryl acrylate;tetrahydrofurfuryl methacrylate; 2,2,2-trifluoroethyl methacrylate;isobornyl methacrylate; polypropylene glycol monomethacrylates,aliphatic urethane acrylate (e.g., RAHN GENOMER 1122); hydroxyethylacrylate; n-lauryl methacrylate; tetrahydrofurfuryl acrylate;2,2,2-trifluoroethyl acrylate; isobornyl acrylate; polypropylene glycolmonoacrylates; trimethylpropane triacrylate; trimethylpropanetrimethacrylate; pentaerythritol tetraacrylate; pentaerythritoltetraacrylate; triethyleneglycol diacrylate; triethylene glycoldimethacrylate; tetrathyleneglycol diacrylate; tetrathylene glycoldimethacrylate; neopentyldimethacrylate; neopentylacrylate; hexanedioldimethacylate; hexane diol diacrylate; polyethylene glycol 400dimethacrylate; polyethylene glycol 400 diacrylate; diethylglycoldiacrylate; diethylene glycol dimethacrylate; ethyleneglycol diacrylate;ethylene glycol dimethacrylate; ethoxylated bis phenol A dimethacrylate;ethoxylated bis phenol A diacrylate; bisphenol A glycidyl methacrylate;bisphenol A glycidyl acrylate; ditrimethylolpropane tetraacrylate; orditrimethylolpropane tetraacrylate.

Particular embodiments provide compositions comprising an acrylatemonomer, e.g., an acrylate monomer, a methacrylate monomer, etc. In someembodiments, the acrylate monomer is an acrylate monomer such as, butnot limited to, (meth)acrylic acid monomers such as (meth)acrylic acid,methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate,isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate,tert-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate,cyclohexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate,2-ethylhexyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate,dodecyl(meth)acrylate, phenyl(meth)acrylate, toluoyl(meth)acrylate,benzyl(meth)acrylate, 2-methoxyethyl(meth)acrylate,3-methoxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate,2-hydroxypropyl(meth)acrylate, stearyl(meth)acrylate,glycidyl(meth)acrylate, 2-aminoethyl(meth)acrylate,3-(methacryloyloxypropyl)trimethoxysilane, (meth)acrylic acid-ethyleneoxide adducts, trifluoromethylmethyl(meth)acrylate,2-trifluoromethylethyl(meth)acrylate,2-perfluoroethylethyl(meth)acrylate,2-perfluoroethyl-2-perfluorobutylethyl(meth)acrylate,2-perfluoroethyl(meth)acrylate, perfluoromethyl(meth)acrylate,diperfluoromethylmethyl(meth)acrylate,2-perfluoromethyl-2-perfluoroethylethyl(meth)acrylate,2-perfluorohexylethyl(meth)acrylate, 2-perfluorodecylethyl(meth)acrylateand 2-perfluorohexadecylethyl(meth)acrylate.

Some embodiments provide a composition comprising n-butyl acrylate,methyl methacrylate, 2-ethylhexyl acrylate, methyl acrylate, tert-butylacrylate, 2-hydroxyethyl acrylate, glycidyl methacrylate, or acombination thereof. However, embodiments of the technology encompasscompositions comprising any acrylate or (meth)acrylate.

In some embodiments, the technology provides a composition comprising amonomer at approximately 1 to 99.99 wt % (e.g., approximately 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.1, 99.2. 99.3,99.4, 99.5, 99.6, 99.7, 99.8, 99.9, 99.95, to 99.99 wt %).

Embodiments of the technology provide a composition comprising aphotoinitiator. The technology is not limited in the photoinitiatorprovided it is chemically compatible with the photoinhibitor compounds(e.g., a photoinhibitor compound having fast back reaction kinetics(e.g., a HABI photoinhibitor (e.g., a bridged HABI photoinhibitor)))described herein. Further, embodiments relate to use of a photoinitiatorthat is optically compatible with the photoinhibitor compounds (e.g., aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor))) described herein.In particular, the technology comprises use of a photoinitiator that isactivated by a wavelength of light that is different than the wavelengthof light that activates the photoinhibitor (e.g., a photoinhibitorcompound having fast back reaction kinetics (e.g., a HABI photoinhibitor(e.g., a bridged HABI photoinhibitor))).

Accordingly, the technology comprises use of a wide variety ofphotoinitiator compounds and irradiation conditions for activating thephotoinitiator to effect the photoinitiation process. Non-limitingexamples of the photoinitiator include benzophenones, thioxanthones,anthraquinones, camphorquinones, thioxanthones, benzoylformate esters,hydroxyacetophenones, alkylaminoacetophenones, benzil ketals,dialkoxyacetophenones, benzoin ethers, phosphine oxides, acyloximinoesters, alphahaloacetophenones, trichloromethyl-S-triazines,titanocenes, dibenzylidene ketones, ketocoumarins, dye sensitizedphotoinitiation systems, maleimides, and mixtures thereof. Particularexamples of photoinitiators include, e.g.,1-hydroxy-cyclohexyl-phenyl-ketone (IRGACURE 184; BASF, Hawthorne,N.J.); a 1:1 mixture of 1-hydroxy-cyclohexyl-phenyl-ketone andbenzophenone (IRGACURE 500; BASF);2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR 1173; BASF);2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (IRGACURE2959; BASF); methyl benzoylformate (DAROCUR MBF; BASF);oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester;oxy-phenyl-acetic 2-[2-hydroxy-ethoxy]-ethyl ester; a mixture ofoxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester andoxy-phenyl-acetic 2-[2-hydroxy-ethoxy]-ethyl ester (IRGACURE 754; BASF);alpha,alpha-dimethoxy-alpha-phenylacetophenone (IRGACURE 651; BASF);2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)-phenyl]-1-butanone(IRGACURE 369; BASF);2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone(IRGACURE 907; BASF); a 3:7 mixture of2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl) phenyl]-1-butanone andalpha,alpha-dimethoxy-alpha-phenylacetophenone per weight (IRGACURE1300; BASF); diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide (DAROCURTPO; BASF); a 1:1 mixture of diphenyl-(2,4,6-trimethylbenzoyl)-phosphineoxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR 4265; BASF);phenyl bis(2,4,6-trimethyl benzoyl) phosphine oxide, which may be usedin pure form (IRGACURE 819; BASF, Hawthorne, N.J.) or dispersed in water(45% active, IRGACURE 819DW; BASF); 2:8 mixture of phosphine oxide,phenyl bis(2,4,6-trimethyl benzoyl) and2-hydroxy-2-methyl-1-phenyl-1-propanone (IRGACURE 2022; BASF); IRGACURE2100, which comprises phenyl-bis(2,4,6-trimethylbenzoyl)-phosphineoxide); bis-(eta5-2,4-cyclopentadien-1-yl)-bis-[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]-titanium (IRGACURE 784; BASF); (4-methylphenyl)[4-(2-methylpropyl)phenyl]-iodonium hexafluorophosphate (IRGACURE 250;BASF);2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-butan-1-one(IRGACURE 379; BASF);4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone (IRGACURE 2959;BASF); bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide;a mixture of bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphineoxide and 2-hydroxy-2-methyl-1-phenyl-propanone (IRGACURE 1700; BASF);4-Isopropyl-9-thioxanthenone; and mixtures thereof.

In some embodiments, the photoinitiator is used in an amount rangingfrom approximately 0.01 to approximately 25 weight percent (wt %) of thecomposition (e.g., from approximately 0.1 to approximately 3.0 wt % ofthe composition (e.g., approximately 0.2 to 0.5 wt % of thecomposition)). In some embodiments, the technology provides acomposition comprising a photoinitiator at approximately 0.01, 0.02,0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14,0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26,0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70,0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5,5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

Embodiments of the technology provide a composition further comprising acoinitiator, e.g., to enhance the polymerization rate, extent, quality,etc. The technology is not limited in the coinitiator. Non-limitingexamples of co-initiators include primary, secondary, and tertiaryamines; alcohols; and thiols. Particular examples of coinitiatorsinclude, e.g., dimethylaminobenzoate, isoamyl 4-(dimethylamino)benzoate,2-ethylhexyl 4-(dimethylamino)benzoate; ethyl 4-(dimethylamino)benzoate;3-(dimethylamino)propyl acrylate; 2-(dimethylamino)ethyl methacrylate;4-(dimethylamino)benzophenones, 4-(diethylamino)benzophenones;4,4′-bis(diethylamino)benzophenones; methyl diethanolamine;triethylamine; hexane thiol; heptane thiol; octane thiol; nonane thiol;decane thiol; undecane thiol; dodecane thiol; isooctyl3-mercaptopropionate; pentaerythritol tetrakis(3-mercaptopropionate);4,4′-thiobisbenzenethiol; trimethylolpropane tris(3-mercaptopropionate);CN374 (SARTOMER); CN371 (SARTOMER), CN373 (SARTOMER), GENOMER 5142(RAHN); GENOMER 5161 (RAHN); GENOMER 5271 (RAHN); GENOMER 5275 (RAHN),and TEMPIC (BRUNO BOC, Germany).

In some embodiments, the coinitiator is used in an amount ranging fromapproximately 0.0 to approximately 25 weight percent (wt %) of thecomposition (e.g., approximately 0.1 to approximately 3.0 wt % of thecomposition (e.g., 0.1 to 1.0 wt %) when used in embodiments of thecompositions). In some embodiments, the technology provides acomposition comprising a coinitiator at approximately 0, 0.01, 0.02,0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14,0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26,0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70,0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5,5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

Some embodiments comprise use of a photon absorbing component, e.g., alight blocking dye (also known as a “photoabsorber”). In someembodiments, a photon absorbing component is selected in accordance withthe wavelengths of the first and second lights. In some embodiments,dyes are used to both attenuate light and to transfer energy tophotoactive species increasing the sensitivity of the system to a givenwavelength for either or both photoinitiation and photoinhibitionprocesses. In some embodiments, the concentration of the chosen dye ishighly dependent on the light absorption properties of the given dye andranges from approximately 0.001 to approximately 5 weight percent (wt %)of the composition. Useful classes of dyes include compounds commonlyused as UV absorbers for decreasing weathering of coatings including,such as, 2-hydroxyphenyl-benzophenones;2-(2-hydroxyphenyl)-benzotriazoles; and 2-hydroxyphenyl-s-triazines.Other useful dyes include those used for histological staining or dyingof fabrics. A non-limiting list includes Martius yellow, Quinolineyellow, Sudan red, Sudan I, Sudan IV, eosin, eosin Y, neutral red, andacid red. Pigments can also be used to scatter and attenuate light.

In some embodiments, the photon absorbing component (e.g., a lightblocking dye) is used in an amount ranging from approximately 0.0 toapproximately 25 weight percent (wt %) of the composition (e.g.,approximately 0.1 to approximately 3.0 wt % of the composition (e.g.,0.1 to 1.0 wt %) when used in embodiments of the compositions). In someembodiments, the technology provides a composition comprising a photonabsorbing component (e.g., a light blocking dye) at approximately 0,0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12,0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24,0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60,0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5,4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

Some embodiments do not comprise a photon absorbing component (e.g., insome embodiments, compositions are “photoabsorber-free”). In particular,embodiments are provided in which compositions are photoabsorber-free toincrease or maximize the penetration of a wavelength of light through acomposition as described herein (e.g., comprising a polymerizablemonomer, a photoinitiator, and a photoinhibitor (e.g., a photoinhibitorcompound having fast back reaction kinetics (e.g., a HABI photoinhibitor(e.g., a bridged HABI photoinhibitor)))).

In some embodiments, a composition further comprises solid particlessuspended or dispersed therein. Any suitable solid particle can be used,depending upon the end product being fabricated. In some embodiments,the solid particles are metallic, organic/polymeric, inorganic, orcomposites or mixtures thereof. In some embodiments, the solid particlesare nonconductive, semi-conductive, or conductive (including metallicand non-metallic or polymer conductors); in some embodiments, the solidparticles are magnetic, ferromagnetic, paramagnetic, or nonmagnetic. Theparticles can be of any suitable shape, including spherical, elliptical,cylindrical, etc.

In some embodiments, a composition comprises a pigment, dye, activecompound, pharmaceutical compound, or detectable compound (e.g.,fluorescent, phosphorescent, radioactive). In some embodiments, acomposition comprises a protein, peptide, nucleic acid (DNA, RNA (e.g.,siRNA)), sugar, small organic compound (e.g., drug and drug-likecompound), etc., including combinations thereof.

In some embodiments, the compositions are homogenous. The technology isrelated to forming polymerized structures; accordingly, in someembodiments, the compositions are heterogeneous because thecompositions, in some embodiments, comprise polymerized andnon-polymerized regions. In some embodiments, compositions of thetechnology comprise a polymer (e.g., comprising polymerized monomers).In some embodiments, a polymerized region is patterned, localized, etc.

Hexaarylbiimidazole (HABI) Compounds for Three-Dimensional Printing

In some embodiments, the technology relates to the use of ahexaarylbiimidazole (HABI) compound as a photoactivated inhibitor ofpolymerization (“photoinhibitor”). Hexaarylbiimidazole (HABI) wasdeveloped in the 1960s as a photochromic molecule by Hayashi and Maeda(see, e.g., Hayashi and Maeda (1960) “Preparation of a new phototropicsubstance” Bull. Chem. Soc. Jpn. 33(4): 565-66, incorporated herein byreference). The general structure of a HABI compound is shown in FIG. 4Aand one particular HABI compound is shown on the left in FIG. 4B. FIG.4B shows: i) the light-induced homolytic cleavage of the HABI C—N bondto produce two radicals (e.g., triphenylimidazolyl radicals (“TPIR”),also known as lophyl radicals); and ii) recombination of the tworadicals in the “back reaction” to reform the HABI imidazole dimer(accordingly, also called a triphenylimidazolyl dimer “TPID”). Therecombination “back reaction” is driven by thermal energy and radicaldiffusion. The lophyl radical has a large absorption band in the visibleregion of the electromagnetic spectrum, whereas HABI absorbs only in theUV region of the electromagnetic spectrum and is therefore colorless.Consequently, HABI generates a colored radical species upon UV lightirradiation and the radicals slowly reform to produce the colorless HABIimidazole dimer when light irradiation is stopped. FIG. 6 showso-chlorohexaarylbiimidazole (o-Cl-HABI), the light-induced reactionforming the chloro-triphenylimidizolyl radicals, and the thermallydriven back reaction to reform the o-Cl-HABI. The halflife of theradicals formed in this reaction is approximately tens of seconds (e.g.,approximately 10 s). Thus, in some embodiments, the technology relatesto an o-chlorohexaarylbiimidazole (o-Cl-HABI) that has a half-life ofapproximately tens of seconds (e.g., approximately 10 s).

Cleavage of the HABI C—N bond by UV irradiation occurs in less than 100fs and is thus nearly (e.g., substantially, effectively) instantaneous;recombination of the radicals to reform HABI is a second order reactionthat occurs over a time of up to a few minutes at room temperature.Thus, the lophyl radicals formed from HABI have a half-life of tens ofseconds to several (e.g., 5 to 10 or more) minutes (see, e.g., Satoh etal. (2007) “Ultrafast laser photolysis study on photodissociationdynamics of a hexaarylbiimidazole derivative” Chem. Phys. Lett. 448(4-6): 228-31; Sathe, et al. (2015) “Re-examining the PhotomediatedDissociation and Recombination Kinetics of Hexaarylbiimidazoles” Ind.Eng. Chem. Res. 54 (16): 4203-12, each of which is incorporated hereinby reference). HABI has been known as a photoinitiator, e.g., forimaging and photoresists. HABI compounds do not initiate on their ownupon formation of radicals. When used as a photoinitiator, the radicalabstracts hydrogen atoms from coinitiator thiol groups (e.g., a crystalviolet precursor) to form an initiating moiety. See, e.g., Dessauer, R.(2006) Photochemistry History and Commercial Applications ofHeaarylbiimidazoles, Elsevier.

In some embodiments, the technology relates to use of a bridged HABI.See, e.g., Iwahori et al. (2007) “Rational design of a new class ofdiffusion-inhibited HABI with fast back-reaction” J Phys Org Chem 20:857-63; Fujita et al. (2008) “Photochromism of a radicaldiffusion-inhibited hexaarylbiimidazole derivative with intensecoloration and fast decoloration performance” Org Lett 10: 3105-08;Kishimoto and Abe (2009) “A fast photochromic molecule that colors onlyunder UV light” J Am Chem Soc 131: 4227-29; Harada et al. (2010)“Remarkable acceleration for back-reaction of a fast photochromicmolecule” J Phys Chem Lett 1: 1112-15; Mutoh et al. (2010) “An efficientstrategy for enhancing the photosensitivity of photochromic[2.2]paracyclophane-bridged imidazole dimers” J Photopolym Sci Technol23: 301-06; Kimoto et al. (2010) “Fast photochromic polymers carrying[2.2]paracyclophane-bridged imidazole dimer” Macromolecules 43: 3764-69;Hatano et al. (2010) “Unprecedented radical-radical reaction of a[2.2]paracyclophane derivative containing an imidazolyl radical moiety”Org Lett 12: 4152-55; Hatano et al. (2011) “Reversible photogenerationof a stable chiral radical-pair from a fast photochromic molecule” JPhys Chem Lett 2: 2680-82; Mutoh and Abe (2011) “Comprehensiveunderstanding of structure-photosensitivity relationships ofphotochromic [2.2]paracyclophane-bridged imidazole dimers” J Phys Chem A115: 4650-56; Takizawa et al. (2011) “Photochromic organogel based on[2.2]paracyclophane-bridged imidazole dimer with tetrapodal ureamoieties” Dyes Pigm 89: 254-59; Mutoh and Abe (2011) “Photochromism of awater-soluble vesicular [2.2]paracyclophane bridged imidazole dimer”Chem Comm 47:8868-70; Yamashita and Abe (2011) “Photochromic propertiesof [2.2]paracyclophane-bridged imidazole dimer with increasedphotosensitivity by introducing pyrenyl moiety” J Phys Chem A 115:13332-37; Kawai et al. (2012) “Entropy-controlled thermal back-reactionof photochromic [2.2]paracyclophane-bridged imidazole dimer” Dyes Pigm92: 872-76; Mutoh et al. (2012) “Spectroelectrochemistry of aphotochromic [2.2]paracyclophane-bridged imidazole dimer: Clarificationof the electrochemical behavior of HABI” J Phys Chem A 116: 6792-97;Mutoh et al. (2013) “Photochromism of a naphthalene-bridged imidazoledimer constrained to the ‘anti’ conformation” Org Lett 15: 2938-41;Shima et al. (2014) “Enhancing the versatility and functionality of fastphotochromic bridged-imidazole dimers by flipping imidazole ring” J AmChem Soc 136: 3796-99; Iwasaki et al. (2014) “A chiral BINOL-bridgedimidazole dimer possessing sub-millisecond fast photochromism” ChemCommun 50: 7481-84; and Yamaguchi et al. (2015) “Nanosecond photochromicmolecular switching of a biphenyl-bridged imidazole dimer revealed bywide range transient absorption spectroscopy” Chem Commun 51: 1375-78,each of which is incorporated herein by reference in its entirety.

Similar to the conventional HABI molecules, the bridged HABI moleculesform radicals instantaneously upon exposure to UV light. However, theradicals are linked by a covalent bond (e.g., one or more covalent bondsand/or, e.g., an R group), which prevents diffusion of the radicals awayfrom one another and thus accelerates the thermally driven reformationof the bridged HABI molecule. Accordingly, the bridged HABI moleculesinstantaneously produce radicals upon UV light irradiation and theradicals rapidly disappear when UV irradiation is stopped.

As used herein, the term “bridged HABI” refers to a HABI molecule inwhich the triphenylimidazolyl radicals are linked (e.g., by one or morecovalent bonds or by an R group) to each other such that they do notdiffuse away from one another upon hemolytic cleavage of the bondconnecting the imidazole centers (e.g., by light). As used herein, theterm “X-bridged HABI”, where “X” refers to an R group (e.g., moiety,chemical group, etc.), refers to a HABI wherein the imidazolyl moietiesare linked by the R group. See, e.g., FIGS. 5A, 5B, 5C, 5D, and 5E. Insome embodiments, the technology relates to the use of a photoinhibitorthat forms inhibiting moieties having a half life shorter than 10seconds (e.g., shorter than 10.0, 9.9, 9.8, 9.7, 9.6, 9.5, 9.4, 9.3,9.2, 9.1, 9.0, 8.9, 8.8, 8.7, 8.6, 8.5, 8.4, 8.3, 8.2, 8.1, 8.0, 7.9,7.8, 7.7, 7.6, 7.5, 7.4, 7.3, 7.2, 7.1, 7.0, 6.9, 6.8, 6.7, 6.6, 6.5,6.4, 6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1,5.0, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7,3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3,2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9,0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.01, 0.001, or 0.0001 seconds).

In an exemplary embodiment, the half-life of the radicals formed from anaphthalene-bridged HABI and a [2.2]paracyclophane-bridged HABI dimerare approximately 830 ms and 33 ms at 25° C. in benzene, respectively.See, e.g., Iwahori et al. (2007) “Rational design of a new class ofdiffusion-inhibited HABI with fast back-reaction” J Phys Org Chem 20:857-63; Fujita et al. (2008) “Photochromism of a radicaldiffusion-inhibited hexaarylbiimidazole derivative with intensecoloration and fast decoloration performance” Org Lett 10: 3105-08;Kishimoto and Abe (2009) “A fast photochromic molecule that colors onlyunder UV light” J Am Chem Soc 131: 4227-29, each of which isincorporated herein in its entirety.

Additional exemplary embodiments relate to use of a HABI in which theimidazole moieties are linked by a 1,1′-bi-naphthol bridge. The1,1′-bi-naphthol-bridged HABI has a half-life of approximately 100 μs.See, e.g., Iwasaki et al. (2014) “A chiral BINOL-bridged imidazole dimerpossessing sub-millisecond fast photochromism” Chem Commun 50: 7481-84,incorporated herein by reference. In some embodiments, the technologyrelates to use of a HABI comprising a bond linking the imidazolyl groups(e.g., a bond links the imidazolyl groups; see, e.g., FIG. 5D) that hasa half-life of approximately 100 ns, which is the fastest thermal backreaction for a HABI compound presently known in the art. See, e.g.,Yamaguchi et al. (2015) “Nanosecond photochromic molecular switching ofa biphenyl-bridged imidazole dimer revealed by wide range transientabsorption spectroscopy” Chem Commun 51: 1375-78, incorporated herein byreference in its entirety.

Accordingly, the technology relates in some embodiments to use ofbridged HABI molecules as photoactivatable inhibitors of polymerization.In some embodiments, the bridged HABI molecules form a radical uponirradiation by light (e.g., at an appropriate wavelength to form aradical from the HABI). In some embodiments, the radical rapidlydisappears upon stopping the irradiation by light. For example,embodiments relate to a bridged HABI that forms a radical having ahalf-life of approximately 100 ns to 100 μs to 100 ms to 100 s (e.g.,10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700,800, 900, or 1000 ns; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300,400, 500, 600, 700, 800, 900, or 1000 μs; 10, 20, 30, 40, 50, 60, 70,80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ms; or 0,20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800,900, or 1000 s). That is, after formation of the radical by irradiationof the bridged HABI at the appropriate wavelength, the radical rapidlyreforms the bridged HABI upon stopping the irradiation. Consequently,the radical is only formed in the region irradiated by the appropriatewavelength to form a radical from the HABI.

Like HABI compounds, bridged HABI compounds do not exhibitphotoinitiation activity when irradiated. Moreover, bridged HABIcompounds do not participate in chain transfer reactions and thuspolymerization rates are not inherently retarded by the presence of HABIcompounds. Finally, bridged HABI compounds typically exhibit very weakabsorbance in the blue region of the electromagnetic spectrum andmoderately absorb in the near-UV region of the electromagnetic spectrum,thus complementing the absorbance spectrum of several photoinitiatorsactivated by blue light. Finally, bridged HABI compounds exhibit fastback reaction kinetics.

Irradiation for Three-Dimensional Printing

Embodiments relate to irradiating polymerizable compositions (e.g.,comprising a polymerizable monomer, a photoinitiator, and aphotoinhibitor (e.g., a photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor)))) with multiple wavelengths of light. In someembodiments, a first wavelength produces initiating radicals from thephotoinitiator and a second wavelength produces inhibiting radicals froma photoinhibitor (e.g., a photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor))). During irradiation, regions (e.g., volumes, areas,etc.) of the composition are exposed to: 1) the first wavelength only;2) the second wavelength only; or 3) both the first and secondwavelengths. Accordingly, polymerization occurs in regions irradiated bythe first wavelength only (e.g., in regions irradiated by the firstwavelength but not irradiated by the second wavelength). And,polymerization is inhibited in regions irradiated by the secondwavelength (e.g., in regions irradiated by the second wavelength and thefirst wavelength; and in regions irradiated by the second wavelength butnot irradiated by the first wavelength). Thus, by providing control ofthe wavelength, intensity, pattern (e.g., cross sectional area, crosssection shape, etc.), and direction of the first and/or secondwavelengths of light (e.g., as provided by one or more sources), thetechnology provides control over the polymerized region in thecomposition. In some embodiments, wavelength, intensity, pattern (e.g.,cross sectional area, cross section shape, etc.), and direction of thefirst and/or second wavelengths of light (e.g., as provided by one ormore sources) is controlled (e.g., varies) as a function of time.

For instance, FIG. 23 shows a diagram exemplifying an embodiment 100 ofthe technology described herein. FIG. 23 shows a cuvette 101 comprisinga composition 102 as described herein, e.g., a composition comprising apolymerizable monomer (e.g., a di(meth)acrylate monomer), aphotoinitiator (e.g., camphorquinone), and a photoinhibitor (e.g., aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor))). In someembodiments, the compositions do not comprise a photoabsorber (e.g., insome embodiments, the composition is photoabsorber-free).

As shown in the exemplary figure, the composition is irradiated by anear-UV light 103 (e.g., approximately 365 nm) to activate thephotoinhibitor in the composition 102. The near-UV light is provided asa pattern to produce a region within the composition having a particularshape that comprises the photoinhibitor. In some embodiments, thepattern is provided by a pattern component 104 such as a mask. FIG. 23shows the source of the near-UV light 103 at the left; in the embodimentshown, the near-UV light passes through a mask or other component 104 toprovide the near-UV light in a pattern that irradiates the compositionto produce the inhibiting moiety (e.g., the inhibiting radical). In theembodiment shown in the figure, the near-UV light 103 irradiates aphotoinhibition region 105 that is a square prism with a non-irradiatedcylindrical volume 106 in its center. Accordingly, the near-UV light 103produces the inhibiting species from the photoinhibitor (e.g., aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor))) within thephotoinhibition region 105 but not within the cylindrical volume 106.

Simultaneously, in the embodiment shown in the exemplary figure, thecomposition is irradiated by a blue light 107 (e.g., approximately 470nm) to activate the photoinitiator in the composition 102. In someembodiments, the blue light 107 is provided as a pattern to produce aregion within the composition having a particular shape that comprisesthe photoinitiator. In some embodiments, the pattern is provided by apattern component 108 such as a mask. FIG. 23 shows the source of theblue light 107 at the top right; in the embodiment shown, the blue lightpasses through a mask or other component 108 to provide the blue lightin a pattern that irradiates the composition to produce the initiatingmoiety (e.g., the initiating radical). In the embodiment shown in thefigure, the blue light 107 irradiates a photoinitiation region 109shaped like a prismatic volume, e.g., having ends shaped like thepatterned light, through the composition. Accordingly, the blue light107 produces the photoinitiator within the photoinitiator region 109.

Accordingly, the polymerizable monomer is polymerized in the regionwithin the composition that is defined in three dimensions as beingboth 1) irradiated by the blue light 107 to form the photoinitiator; and2) not irradiated by the near-UV light 103 to form the photoinhibitor.Thus, according to the technology, a three-dimensional item ofpolymerized material is formed instantaneously within the compositionwithout forming a series of stacked two-dimensional slabs in alayer-by-layer process. Furthermore, according to the technology,three-dimensional item of polymerized material is buoyant within thecomposition and thus portions of the polymerized item that might bebroken, distorted, or otherwise deformed by gravity or other forces aresupported by buoyancy and, in some embodiments, the technologyconsequently does not require structural supports for polymerized items.

While FIG. 23 depicts an illustrative embodiment of the technology, thetechnology is not limited to the features and aspects shown therein ordiscussed herein in reference to FIG. 4.

For instance, the technology is not limited in the light used forirradiation and/or the light sources that are used for irradiation,e.g., a light having a first wavelength and a light having a secondwavelength. The technology is not limited in the direction and/orrelative angle of the sources providing the first and secondwavelengths. The technology is not limited in the cross sectionalshapes, areas, and/or patterns of the first and/or second wavelengths orthe intensities of the first and/or second wavelengths. The technologyis not limited in the wavelengths of the first and/or second sources.

As noted herein, the technology is not limited in the source of thelight (e.g., one or more sources of one or more wavelengths of light).Accordingly, embodiments of the technology comprise, and comprise useof, a suitable light source (or combination of light sources) selectedto be appropriate for the particular monomer (“resin”), photoinitiator,and/or photoinhibitor employed. While embodiments are discussed in termsof a light source, embodiments also include sources of radiationincluding an electron beam and other ionizing radiation sources.

In some embodiments, the light source is an actinic radiation source,such as one or more light sources (e.g., one or more light sourcesproviding visible and/or ultraviolet electromagnetic radiation). In someembodiments, a light source is, e.g., an incandescent light, fluorescentlight, phosphorescent or luminescent light, laser, light-emitting diode,etc., including arrays thereof. In some embodiments, a light sourceprovides even coverage of light. Accordingly, in some embodiments alight source is a collimated beam or a planar waveguide, e.g., toprovide even coverage of a light.

In some embodiments, the first wavelength is produced by a first lightsource, and the second wavelength is produced by a second light source.In some embodiments, the first wavelength and the second wavelength areproduced by the same light source. In some embodiments, the firstwavelength and second wavelength have emission peak wavelengths that areat least 5 or 10 nm apart from one another (e.g., the emission peak ofthe first wavelength is at least 5, 6, 7, 8, 9, 10, or more nm apartfrom the emission peak of the second wavelength).

In particular, as discussed herein, the technology relates to use of afirst wavelength to activate a photoinitiator. Activating thephotoinitiator produces an initiating moiety (e.g., initiating radicals)from the photoinitiator. The initiating radicals initiate polymerizationof the polymerizable monomers. Further, as discussed herein, thetechnology relates to use of a second wavelength to activate aphotoinhibitor (e.g., a photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor))). Activating the photoinhibitor produces an inhibitingmoiety (e.g., inhibiting radicals) from the photoinhibitor. Theinhibiting radicals prevent polymerization of the polymerizablemonomers. Accordingly, embodiments of the technology relate to use of 1)a first wavelength of light that activates the photoinitiator and thatdoes not activate the photoinhibitor; and 2) a second wavelength oflight that activates the photoinitiator and that does not activate thephotoinhibitor. Thus, the photoinhibitor, photoinitiator, firstwavelength, and second wavelength are chosen such that: 1) the firstwavelength of light activates the photoinitiator and does not activatethe photoinhibitor; and 2) the second wavelength of light activates thephotoinhibitor and does not activate the photoinhibitor.

In some embodiments, the first wavelength is at or near the peak of theabsorbance spectrum of the photoinitiator, e.g., within 50 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) of thepeak of the absorbance spectrum of the photoinitiator. In someembodiments, the second wavelength is at or near the peak of theabsorbance spectrum of the photoinhibitor, e.g., within 50 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) of thepeak of the absorbance spectrum of the photoinhibitor.

A wavelength of light that is not strongly absorbed penetrates moredeeply into a composition comprising an absorbing compound (e.g., aphotoinitiator or photoinhibitor) and therefore activates a largervolume of photoactivated compound (e.g., a photoinitiator orphotoinhibitor). Accordingly, in some embodiments, the first wavelengthis chosen to be a wavelength that activates the photoinitiator, but thatis also not strongly absorbed by the photoinitiator; similarly, in someembodiments, the second wavelength is chosen to be a wavelength thatactivates the photoinhibitor, but that is also not strongly absorbed bythe photoinhibitor.

In some embodiments, the first wavelength is not near the peak of theabsorbance spectrum of the photoinitiator, e.g., at least 50 nm (e.g.,at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) away fromthe peak of the absorbance spectrum of the photoinitiator. In someembodiments, the second wavelength is not near the peak of theabsorbance spectrum of the photoinhibitor, e.g., at least 50 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) away fromthe peak of the absorbance spectrum of the photoinhibitor. Similarly, insome embodiments, the absorbance of the photoinitiator at the firstwavelength is less than 25% (e.g., less than 25, 24, 23, 22, 21, 20, 19,18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4.5, 4, 3.5, 3, 2.5,2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6,0.5, 0.4, 0.3, 0.2, 0.1, or 0.05%) of the absorbance of thephotoinitiator at the wavelength of the absorbance peak of thephotoinitiator. And, in some embodiments, the absorbance of thephotoinhibitor at the second wavelength is less than 25% (e.g., lessthan 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9,8, 7, 6, 5, 4.5, 4, 3.5, 3, 2.5, 2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3,1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, or 0.05%) ofthe absorbance of the photoinhibitor at the wavelength of the absorbancepeak of the photoinhibitor.

In some embodiments, a first light source initiates polymerization ofmonomers in a polymerizable composition. Further, a second light sourceproviding a different wavelength of light is provided to inhibit (e.g.,prevent) and spatially restrict polymerization of monomers in thepolymerizable composition. In some embodiments, the first and secondlight sources irradiate overlapping regions of the composition. In someembodiments, the first and second light sources irradiate adjacentregions of the composition. In some embodiments, the first and secondlight sources irradiate different regions of the composition. In someembodiments, the shape and/or size of a polymerized region is determinedby the difference of the photoinitiating pattern of the first lightsource and the photoinhibiting pattern of the second light source.

In some embodiments, light is provided in a pattern. In someembodiments, the first wavelength of light is provided as a pattern. Insome embodiments, the second wavelength of light is provided as apattern. The first and second wavelengths may be provided in patternsthat are the same or different. In some embodiments, the methodscomprise irradiating a composition as described herein with a pattern ofa first wavelength of light. In some embodiments, the methods compriseirradiating a composition as described herein with a pattern of a secondwavelength of light. In some embodiments, different patterns of lightfor two different wavelengths of light are used. In some embodiments,the patterns overlap in different configurations. In some embodiments,the methods comprise irradiating a composition as described herein witha first pattern of a first wavelength of light. In some embodiments, themethods comprise irradiating a composition as described herein with asecond pattern of a second wavelength of light.

In some embodiments, the technology provides a pattern having aresolution with millions of pixel elements. In some embodiments, thetechnology provides a pattern having millions of pixel elements whosewavelength and/or intensities are varied to change the pattern ofirradiation provided to the composition. For example, in someembodiments the pattern is provided by a DLP comprising more than 1,000(e.g., more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50thousand or more) rows and/or more than 1,000 (e.g., more than 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 thousand or more) columns. Insome embodiments the pattern is provided by a LCD comprising more than1,000 (e.g., more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or50 thousand or more) rows and/or more than 1,000 (e.g., more than 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 thousand or more) columns.

In some embodiments, a light source is a liquid crystal display (LCD),light emitting diode (LED), or a digital light projector (DLP), e.g., todeliver a pattern of light. In some embodiments, the light sourceincludes a pattern-forming element operatively associated with acontroller. In some embodiments, the light source or pattern formingelement comprises a digital (or deformable) micromirror device (DMD)with digital light processing (DLP), a spatial modulator (SLM), or amicroelectromechanical system (MEMS) mirror array, a mask (aka areticle), a silhouette, or a combination thereof. See, U.S. Pat. No.7,902,526, incorporated herein by reference. In some embodiments, thelight source comprises a spatial light modulation array such as a liquidcrystal light valve array or micromirror array or DMD (e.g., with anoperatively associated digital light processor, typically under thecontrol of a suitable controller), configured to carry out exposure orirradiation of a composition as described herein (e.g., by masklessphotolithography). See, e.g., U.S. Pat. Nos. 6,312,134; 6,248,509;6,238,852; and 5,691,541, each of which is incorporated herein byreference.

In some embodiments, the technology provides a pattern having aresolution with millions of pixel elements. In some embodiments, thetechnology provides a pattern having millions of pixel elements whosewavelength and/or intensities are varied to change the pattern ofirradiation provided to the composition. For example, in someembodiments the pattern is provided by a DLP comprising more than 1,000(e.g., more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50thousand or more) rows and/or more than 1,000 (e.g., more than 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 thousand or more) columns. Insome embodiments the pattern is provided by a LCD comprising more than1,000 (e.g., more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or50 thousand or more) rows and/or more than 1,000 (e.g., more than 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 thousand or more) columns.

The technology is not limited in the pattern of irradiation produced bya first and/or second light source. For example, in some embodiments,the pattern comprises one or more geometric shapes, one or moreirregular shapes, or one or more lines, dots, or other graphic features.In some embodiments, the pattern of irradiation changes with time, e.g.,in some embodiments the pattern of irradiation is provided as a seriesof patterned images, e.g., a movie.

For example, in some embodiments, the technology comprises use ofirradiation provided as a time-variable pattern of the first and/orsecond wavelength. In some embodiments, the length of time that eachpattern of irradiation is provided depends on, e.g., the wavelengthand/or intensity of the wavelength, the presence or absence of a photonabsorbing substance (e.g., a dye) in the composition, the photoinitiatorused, the photoinhibitor used (e.g., a photoinhibitor compound havingfast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor)))), and the volume of the composition(e.g., the dimensions of the composition (e.g., in the direction inwhich the light is travelling)). In some embodiments, a composition isirradiated by a pattern for a time that is approximately 1 ps to 6,000seconds or more (e.g., approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5,or 1 ns; approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 μs;approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 ms; approximately0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 s; or approximately 0.001,0.005, 0.01, 0.05, 0.1, 0.5, or 1 μs; approximately 0.001, 0.005, 0.01,0.05, 0.1, 0.5, or 1 minute).

In some embodiments, a “dark” period is provided between eachirradiation pattern. That is, in some embodiments, the composition isnot irradiated for a period of time between the time periods ofirradiation by the first and/or second wavelength. In some embodiments,the period of time during which the composition is not irradiatedbetween periods of irradiation is approximately 1 ns to 6,000 seconds ormore (e.g., approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 ns;approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 μs; approximately0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 ms; approximately 0.001, 0.005,0.01, 0.05, 0.1, 0.5, or 1 s; or approximately 0.001, 0.005, 0.01, 0.05,0.1, 0.5, or 1 μs; approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or1 minute). In some embodiments, the period of time during which thecomposition is not irradiated between periods of irradiation isapproximately 0.1 ps to 1 second (e.g., approximately 0.001, 0.002,0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04,0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9 or 1 ps; approximately 0.001, 0.002, 0.003, 0.004, 0.005, 0.006,0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08,0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 ns; approximately0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9 or 1 μs; or approximately 0.001, 0.002, 0.003, 0.004,0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 s).Thus, in some embodiments, the pattern varies tens, hundreds, thousands,or millions of times to produce a polymerized article within thecomposition.

The technology is not limited in the intensity of the first and/orsecond wavelengths provided by the first and/or second sources. Forexample, embodiments comprise light provided at intensities of from0.001 to 1000 mW/cm² (e.g., approximately 0.001, 0.005, 0.01, 0.05, 0.1,0.5, 1, 5, 10, 50, 100, 500, or 1000 mW/cm²). In some embodiments, lightis provided having a wavelength in the UV, visible, and/or infraredregions of the electromagnetic spectrum (e.g., wavelengths of 10 nm to 1mm (e.g., 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 105, 110, 115, 120,125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190,195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260,265, 270, 275, 280, 285, 290, 295, 300, 305, 310, 315, 320, 325, 330,335, 340, 345, 350, 355, 360, 365, 370, 375, 380, 385, 390, 395, 400,405, 410, 415, 420, 425, 430, 435, 440, 445, 450, 455, 460, 465, 470,475, 480, 490, 495, 500, 505, 510, 515, 520, 525, 530, 535, 540, 545,550, 555, 560, 565, 570, 575, 580, 585, 590, 595, 600, 605, 610, 615,620, 625, 630, 635, 640, 645, 650, 655, 660, 665, 670, 675, 680, 685,690, 695, 700, 705, 710, 715, 720, 725, 730, 735, 740, 745, 750, 755,760, 765, 770, 775, 780, 785, 790, 795, 800, 805, 810, 815, 820, 825,830, 835, 840, 845, 850, 855, 860, 865, 870, 875, 880, 885, 890, 895,900, 905, 910, 915, 920, 925, 930, 935, 940, 945, 950, 955, 960, 965,970, 975, 980, 985, 990, 995, or 1000 nm)).

The technology is not limited in the cross sectional area of the beamand/or two-dimensional pattern that is provided (e.g., the beam orpattern of the first and/or second wavelengths of light provided by thefirst and/or second sources). For example, in some embodiments the crosssectional area of the beam and/or two-dimensional pattern of the firstand/or second wavelength is approximately 0.5 μm² to 10,000 mm² (e.g.,approximately 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800,900, or 1000 μm²; approximately 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500,600, 700, 800, 900, or 1000 mm²; or approximately 0.5, 0.6, 0.7, 0.8,0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100,200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000,6000, 7000, 8000, 9000, or 10,000 mm²). In some embodiments, the crosssectional area of the beam and/or two-dimensional pattern that isprovided (e.g., the beam or pattern of the first and/or secondwavelengths of light provided by the first and/or second sources) isvaried (e.g., increased, decreased) with time.

The technology is not limited in the orientation of the direction ofpropagation of the first and/or second wavelengths from the first and/orsecond sources to the composition. The technology is not limited in theangle between the direction of propagation of the first and secondwavelengths from the first and second sources to the composition. Forexample, in some embodiments the first and second wavelengths areparallel (e.g., and may have the same or different intensities). In someembodiments, the first and second wavelengths are perpendicular. In someembodiments, the first and second wavelengths are antiparallel (e.g.,provided at a 180° angle between the direction of propagation of thefirst and second wavelengths from the first and second sources to thecomposition). The technology comprises embodiments in which the firstand second wavelengths are provided from the first and second sourceswith an angle of 0-180° between them (e.g., 0, 5, 10, 15, 20, 25, 30,35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115,120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, or 180°between them). Some embodiments comprise changing the angle ofpropagation of the first and/or second wavelengths from the first and/orsecond source to the composition. Some embodiments comprise changing theangle of propagation of the first and/or second wavelengths from thefirst and/or second source to the composition as a function of time.

In some embodiments, irradiation as described herein finds use inmethods of producing an item comprising a polymer, e.g., by thepolymerization of polymerizable monomers. Thus, in some embodiments thetechnology comprises irradiating a composition, e.g., with a firstand/or a second wavelength, e.g., as provided by a first and/or a secondwavelength of light. Embodiments of methods comprising irradiating stepsare described herein.

Methods for Three-Dimensional Printing

The technology provides embodiments of methods. In particular, thetechnology relates to methods of producing a polymer, e.g., byirradiating a composition comprising a polymerizable monomer, aphotoinitiator, and a photoinhibitor (e.g., a photoinhibitor compoundhaving fast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor))) with a first wavelength of light (e.g.,to produce an initiating moiety (e.g., an initiating radical) from thephotoinitiator) and a second wavelength of light (e.g., to produce aninhibiting moiety (e.g., an inhibiting radical) from a photoinhibitor(e.g., a photoinhibitor compound having fast back reaction kinetics(e.g., a HABI photoinhibitor (e.g., a bridged HABI photoinhibitor))).Accordingly, methods comprise irradiating the composition with the firstand second wavelengths to produce arbitrary three-dimensional objectscomprising polymer.

In some embodiments, methods comprise providing a composition comprisinga polymerizable monomer, a photoinitiator, and a photoinhibitor (e.g., aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor))). In someembodiments, methods comprise providing a reaction container (e.g., avessel such as a cuvette). In some embodiments, the reaction chambercomprises a composition as described herein. In some embodiments, thereaction chamber is transparent to the first and/or second wavelengthsof light used to irradiate the composition. In some embodiments, thechamber comprises a material that provides a band pass filter, e.g., totransmit to the composition a selected wavelength or range ofwavelengths of light (e.g., as provided by the first and/or secondsources of light).

In some embodiments, methods comprise a step of irradiating thecomposition with a first wavelength of light, e.g., to initiatepolymerization of monomers by producing a radical from thephotoinitiator. In some embodiments, methods comprise a step ofirradiating the composition with a second wavelength of light, e.g., toprevent, inhibit, minimize, and/or stop polymerization of monomers byproducing a radical from a photoinhibitor (e.g., a photoinhibitorcompound having fast back reaction kinetics (e.g., a HABI photoinhibitor(e.g., a bridged HABI photoinhibitor))). Thus, in some embodiments, afirst wavelength of light is focused on a composition as providedherein, e.g., to polymerize a polymerizable monomer in the composition(“photoinitiation”). In some embodiments, a second, different wavelengthof light is focused on a composition as provided herein, e.g., toprevent, inhibit, minimize, and stop the polymerization of thepolymerizable monomer (“photoinhibition”). In the embodiments ofmethods, the first and second wavelengths and/or the first and secondsources are provided as described herein.

In some embodiments, the first wavelength is produced by a first lightsource, and the second wavelength is produced by a second light source.Thus, in some embodiments, methods comprise producing a first wavelengthand, in some embodiments, methods comprise producing a secondwavelength.

In some embodiments, the shape and/or size of a polymerized region isdetermined by the difference of the photoinitiating pattern of the firstlight source and the photoinhibiting pattern of the second light source.

In some embodiments, methods comprise providing a first wavelength in apattern (e.g., a first pattern). In some embodiments, methods compriseproviding a second wavelength in a pattern (e.g., a second pattern). Insome embodiments, the first and/or second patterns are a time-variablepattern as described herein.

In some embodiments, the methods comprise moving a first wavelength oflight and a second wavelength of light to move the region of thecomposition irradiated by the first wavelength, second wavelength,and/or both the first and second wavelengths, e.g., as a function oftime.

In some embodiments, methods comprise inhibiting, preventing,terminating, minimizing, and/or inhibiting polymerization in a region ofthe composition. In some embodiments, methods comprise inhibiting,preventing, terminating, minimizing, and/or inhibiting polymerization byirradiating a region of the composition with the second wavelength oflight, e.g., as provided by a second light source. In some embodiments,photoinhibition of polymerization is rapidly eliminated in the absenceof the photoinhibition irradiation wavelength because the photoinhibitorhaving fast back reaction kinetics reforms from the inhibiting radicalwith a half-life of approximately 100 ns to 100 μs to 100 ms to 100 s(e.g., 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600,700, 800, 900, or 1000 ns; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200,300, 400, 500, 600, 700, 800, 900, or 1000 μs; 10, 20, 30, 40, 50, 60,70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ms; or0, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700,800, 900, or 1000 s). In some embodiments, while the photoinhibitor(e.g., a photoinhibitor compound having fast back reaction kinetics(e.g., a HABI photoinhibitor (e.g., a bridged HABI photoinhibitor)) andinhibiting species formed therefrom are incapable of initiating freeradical polymerization of polymerizable monomers (e.g., methacrylatemonomers), the inhibiting species rapidly recombine with and terminatethe growing polymer chain. Accordingly, in some embodiments, methodscomprise inhibiting, preventing, terminating, minimizing, and/orinhibiting polymerization.

In some embodiments, the methods further comprise varying the intensityof the first wavelength of light. In some embodiments, the methodsfurther comprise varying the intensity of the second wavelength oflight. In some embodiments, varying the intensity of the first and/orsecond wavelength of light changes the region of the composition inwhich polymerization occurs.

In some embodiments, the methods comprise varying the intensity and/orthe wavelength of the first source of light. In some embodiments, themethods further comprise varying the intensity and/or wavelength of thesecond source of light. In some embodiments, varying the intensityand/or wavelength of the first and/or second sources of light changesthe region of the composition in which polymerization occurs.

In some embodiments, methods comprise a step of irradiating thecomposition with a first source of light, e.g., to initiatepolymerization of monomers by producing a radical from thephotoinitiator. In some embodiments, methods comprise a step ofirradiating the composition with a second source of light, e.g., toprevent, terminate, minimize, and/or inhibit polymerization of monomersby producing a radical from a photoinhibitor (e.g., a photoinhibitorcompound having fast back reaction kinetics (e.g., a HABI photoinhibitor(e.g., a bridged HABI photoinhibitor))). In some embodiments, methodscomprise a step of irradiating the composition with a first source oflight, e.g., to produce a region (e.g., a three-dimensional region)within the composition where monomers polymerize. In some embodiments,methods comprise a step of irradiating the composition with a secondsource of light, e.g., to produce a region (e.g., a three-dimensionalregion) within the composition where monomers do not polymerize. In someembodiments, a region irradiated by both the first source of light andthe second source of light is a region within the composition wheremonomers do not polymerize because the initiating radicals do notinitiate polymerization in the presence of the inhibiting radicals.Accordingly, embodiments of the technology comprise producing apolymerization region. In some embodiments, methods comprise producing atime-variable polymerization region within the composition.

In some embodiments, methods comprise irradiating a composition asprovided herein with a first wavelength and/or a second wavelength for atime that is approximately 1 ns to 6,000 seconds or more (e.g.,approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 μs; approximately0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 ms; approximately 0.001, 0.005,0.01, 0.05, 0.1, 0.5, or 1 s; or approximately 0.001, 0.005, 0.01, 0.05,0.1, 0.5, or 1 μs; approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or1 minute). Some embodiments comprise providing periods of time whereinthe composition is not irradiated, e.g., in some embodiments, methodscomprise not irradiating the composition for a period of time betweensubsequent steps of irradiating the composition by the first and/orsecond wavelength. In some embodiments, the period of time of notirradiating the composition, e.g., between periods of irradiating thecomposition, is approximately 1 ns to 6,000 seconds or more (e.g.,approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 ns; approximately0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 μs; approximately 0.001, 0.005,0.01, 0.05, 0.1, 0.5, or 1 ms; approximately 0.001, 0.005, 0.01, 0.05,0.1, 0.5, or 1 s; or approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5,or 1 μs; approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 minute).In some embodiments, the period of time during which the composition isnot irradiated between periods of irradiation is approximately 0.1 ps to1 second (e.g., approximately 0.001, 0.002, 0.003, 0.004, 0.005, 0.006,0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08,0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 ps; approximately0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9 or 1 ns; approximately 0.001, 0.002, 0.003, 0.004,0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 μs;or approximately 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008,0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2,0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 s). Thus, in some embodiments,the pattern varies tens, hundreds, thousands, or millions of times toproduce a polymerized article within the composition.

Some embodiments comprise constantly irradiating with the firstwavelength of light and varying the second wavelength of light. Someembodiments comprise constantly irradiating with the second wavelengthof light and varying the first wavelength of light. Some embodimentscomprise irradiating a composition as described herein with a firstsource providing one or more of a constant intensity, wavelength, and/orpattern of light and irradiating the composition as described hereinwith a second source providing one or more of a varying intensity,wavelength, and/or pattern of light. Some embodiments compriseirradiating a composition as described herein with a second sourceproviding one or more of a constant intensity, wavelength, and/orpattern of light and irradiating the composition as described hereinwith a first source providing one or more of a varying intensity,wavelength, and/or pattern of light.

In some embodiments, methods comprise producing a polymerizing region ina composition comprising a polymerizable monomer, a photoinitiator, anda photoinhibitor (e.g., a photoinhibitor compound having fast backreaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridged HABIphotoinhibitor))). In some embodiments, the polymerizing region is athree-dimensional space contacted by light having a wavelength andintensity that activates the photoinitiator; in some embodiments, thepolymerizing region is not contacted by light having an intensity and/orwavelength that activates the photoinhibitor. That is, in someembodiments the polymerizing region comprises sufficient photoinitiatingradicals to produce polymer from monomer but does not comprisesufficient photoinhibitor to inhibit production of polymer from monomer.

As described herein, the size, wavelength, intensity, and pattern of thefirst and second wavelengths of light produce the three-dimensionalspace in the composition that is the polymerizing region. In someembodiments, the three-dimensional space has dimensions of approximately0.5 μm-100 cm×0.5 μm-100 cm×0.5 μm-100 cm. Accordingly, thethree-dimensional space is shaped, in various embodiments, as a dot, athin rod or line, a slab, a prism, or a cube. The shape of thepolymerizing region, however, is not limited to these particularlylisted shapes and can be any arbitrary shape produced by theintersecting patterns of the first and second wavelengths of light. Insome embodiments, methods comprise varying the polymerizing region as afunction of time, e.g., varying the shape, volume, position, etc. of thepolymerizing region.

Systems for Three-Dimensional Printing

In some embodiments, the technology relates to systems, e.g., comprisinga composition as described herein, a first wavelength of light (e.g., asproduced by a first light source), and a second wavelength of light(e.g., as produced by a second light source).

For instance, system embodiments comprise one or more suitable lightsources selected to be appropriate for the particular monomer (“resin”),photoinitiator, and/or photoinhibitor. While embodiments are discussedin terms of one or more light sources, embodiments also include sourcesof radiation including an electron beam and other ionizing radiationsources. In some embodiments, the first and second wavelengths of lightare produced from the same light source and in some embodiments thefirst and second wavelengths are produced from a first and second lightsource. The various types of light sources are described herein and thefirst and second light sources are independently selected and need notbe the same but may be.

In some embodiments, a light source is an actinic radiation source(e.g., one or more light sources providing visible and/or ultravioletelectromagnetic radiation). In some embodiments, a light source is,e.g., an incandescent light, fluorescent light, phosphorescent orluminescent light, laser, light-emitting diode, etc., including arraysof any of the foregoing. In some embodiments, a light source provideseven coverage of light. Accordingly, in some embodiments a light sourceis a collimated beam or a planar waveguide, e.g., to provide evencoverage of a light.

In some embodiments, systems comprise one or more filters, e.g., totransmit to the composition a selected wavelength or range ofwavelengths of light (e.g., as provided by the first and/or secondsources of light).

In some embodiments, embodiments, systems comprise one or more masks,e.g., to irradiate a composition with a first and/or second wavelengthof light in a specific shape or pattern.

In some embodiments, light is provided in a pattern. Accordingly, insome embodiments a light source is a liquid crystal display (LCD), lightemitting diode (LED), or a digital light projector (DLP), e.g., todeliver a pattern of light. In some embodiments, the light sourceincludes a pattern-forming element operatively associated with acontroller. In some embodiments, the light source or pattern formingelement comprises a digital (or deformable) micromirror device (DMD)with digital light processing (DLP), a spatial modulator (SLM), or amicroelectromechanical system (MEMS) mirror array, a mask (aka areticle), a silhouette, or a combination thereof. See, U.S. Pat. No.7,902,526, incorporated herein by reference. In some embodiments, thelight source comprises a spatial light modulation array such as a liquidcrystal light valve array or micromirror array or DMD (e.g., with anoperatively associated digital light processor, typically in turn underthe control of a suitable controller), configured to carry out exposureor irradiation of a composition as described herein (e.g., by masklessphotolithography). See, e.g., U.S. Pat. Nos. 6,312,134; 6,248,509;6,238,852; and 5,691,541, incorporated herein by reference.

In some embodiments, a light source directs a first light and/or asecond light into a composition as described herein. In someembodiments, the second light has a second wavelength selected toproduce photoinhibition (e.g., to create a photoinhibition layer and/orto create a photoinhibition volume) within the liquid. The first lighthas a first wavelength, different than the second wavelength, that isused to polymerize the photoactive resin in the liquid (e.g., within aphotoinitiation layer). In some embodiments, the first light has a firstwavelength that produces an initiating radical from the photoinitiatorand the second light has a second wavelength, different than the firstwavelength, that forms a radical from a bridged HABI photoinhibitorcompound. In some embodiments, the first and/or second light(s) areprovided in accordance with a defined pattern or patterns. In addition,various embodiments provided that the one or more light sources can be adual wavelength illumination source device or separate illuminationdevices.

In some embodiments, systems comprise a reaction container (e.g., avessel such as a cuvette). In some embodiments, the reaction chambercomprises a composition as described herein. In some embodiments, thereaction chamber is transparent to the first and/or second wavelengthsof light used to irradiate the composition. In some embodiments, thechamber comprises a material that provides a band pass filter, e.g., totransmit to the composition a selected wavelength or range ofwavelengths of light (e.g., as provided by the first and/or secondsources of light).

In some embodiments, the one or more light sources is/are connected witha computer (or other controller). In some embodiments, the technologycomprises use of a computer and/or microprocessor. For example,embodiments of technology are implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, includingembodiments of methods described herein. For example, embodiments of thetechnology are implemented using one or more modules of computer programinstructions encoded on a computer-readable medium for execution by, orto control the operation of, data processing apparatus. Thecomputer-readable medium can be a manufactured product, such as harddrive in a computer system or an optical disc sold through retailchannels, or an embedded system. The computer-readable medium can beacquired separately and later encoded with the one or more modules ofcomputer program instructions, such as by delivery of the one or moremodules of computer program instructions over a wired or wirelessnetwork. The computer-readable medium can be a machine-readable storagedevice, a machine-readable storage substrate, a memory device, or acombination of one or more of them.

In some embodiments, the technology comprises use of a “data processingapparatus”. The term “data processing apparatus” encompasses allapparatus, devices, and machines for processing data, including by wayof example a programmable processor, a computer, or multiple processorsor computers. The apparatus can include, in addition to hardware, codethat creates an execution environment for the computer program inquestion, e.g., code that constitutes processor firmware, a protocolstack, a database management system, an operating system, a runtimeenvironment, or a combination of one or more of them. In addition, theapparatus can employ various different computing model infrastructures,such as web services, distributed computing and grid computinginfrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A computer program does notnecessarily correspond to a file in a file system. A program can bestored in a portion of a file that holds other programs or data (e.g.,one or more scripts stored in a markup language document), in a singlefile dedicated to the program in question, or in multiple coordinatedfiles (e.g., files that store one or more modules, sub-programs, orportions of code). A computer program can be deployed to be executed onone computer or on multiple computers that are located at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

The processes and logic flows described herein can be performed by,and/or under the control of, one or more programmable processorsexecuting one or more computer programs to perform functions byoperating on input data and generating output. The processes and logicflows can also be performed by, and apparatus can also be implementedas, special purpose logic circuitry, e.g., an FPGA (field programmablegate array) or an ASIC (application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto-optical disks, or optical disks. However, a computerneed not have such devices. Moreover, a computer can be embedded inanother device, e.g., a mobile telephone, a personal digital assistant(PDA), a mobile audio or video player, a game console, a GlobalPositioning System (GPS) receiver, or a portable storage device (e.g., auniversal serial bus (USB) flash drive), etc. Devices suitable forstoring computer program instructions and data include all forms ofnon-volatile memory, media and memory devices, including by way ofexample semiconductor memory devices, e.g., EPROM, EEPROM, and flashmemory devices; magnetic disks, e.g., internal hard disks or removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,special purpose logic circuitry.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input.

Some embodiments of the technology are implemented in a computing systemthat includes a back-end component, e.g., as a data server, or thatincludes a middleware component, e.g., an application server, or thatincludes a front-end component, e.g., a client computer having agraphical user interface or a web browser through which a user caninteract with an implementation of the subject matter described is thisspecification, or any combination of one or more such back-end,middleware, or front-end components. The components of the system can beinterconnected by any form or medium of digital data communication,e.g., a communication network. Examples of communication networksinclude a local area network (“LAN”) and a wide area network (“WAN”), aninter-network (e.g., the Internet), and peer-to-peer networks (e.g., adhoc peer-to-peer networks).

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

A computer includes a processor and a memory. The processor can be oneor more hardware processors, which can each include multiple processorcores. The memory can include both volatile and non-volatile memory,such as Random Access Memory (RAM) and Flash RAM. The computer caninclude various types of computer storage media and devices, which caninclude the memory, to store instructions of programs that run on theprocessor. For example, a 3D printing program can be stored in thememory and run on the processor to implement the techniques describedherein.

Uses for Three-Dimensional Printing

The technology is not limited in its use and finds use in a wide varietyof polymer-associated technologies. In some embodiments, thecompositions, methods, and systems described herein are particularlyuseful for making three-dimensional articles. For instance, thetechnology described herein (e.g., related to using dual-wavelengthirradiation) finds use in three-dimensional printing. In contrast toconventional three dimensional (3D) printing based on additivemanufacturing by the accretion of construction material, the presenttechnology provides, in some embodiments, for the production ofpolymerized articles in toto using a single exposure by the first and/orsecond wavelengths to produce the polymerization region of the desiredshape. In some embodiments, a 3D printed object is created by utilizingcomputer-aided design (CAD) data of an object to control sequentialirradiation of a composition as provided herein with constant and/orchanging patterns, wavelengths, and/or intensities of the first and/orsecond wavelengths of light.

In some embodiments, the technology finds use to improve additivemanufacturing method in which two-dimensional slabs are polymerized andadded in succession to produce a three-dimensional object. In someembodiments, the technology finds use in producing the two-dimensionalslabs that are the basis of additive 3D printing.

In some embodiments, the technology finds use in continuous layerinterface production (CLIP). In particular, in some embodiments, the useof the first wavelength, second wavelength, and a composition asdescribed herein (e.g., comprising a photoinhibitor (e.g., aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)))) finds use inproducing a dead zone in CLIP. See, e.g., U.S. Pat. Nos. 9,205,601;9,216,546; and U.S. Pat. App. Pub. No. 2016/0067921, each of which isincorporated herein by reference. In particular, the two-wavelengthphotoinitiator/photoinhibitor technology provided herein finds use inthe three-dimensional printing technology described in U.S. Pat. App.Pub. No. 2016/0067921. In some embodiments, TED used in U.S. Pat. App.Pub. No. 2016/0067921 is replaced by another photoinhibitor (e.g., aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor))).

In some embodiments, the technology finds use in stereolithography (SL).SL is one type of additive manufacturing where a liquid resin ishardened by selective exposure to a radiation to form each 2D layer. Insome embodiments, the radiation is in the form of electromagnetic waves(e.g., light, photons) or an electron beam. The most commonly appliedenergy source is ultraviolet, visible, or infrared radiation. The liquidphotopolymer resin can contain monomers, oligomers, fillers andadditives such as photoinitiators, blockers, colorants and other typesdepending on the targeted properties of the resin.

In some embodiments, the technology finds use in true additivemanufacturing and/or in direct write lithography. Products that may beproduced by the compositions, methods, and systems described hereininclude, but are not limited to, large-scale models or prototypes, smallcustom products, miniature or microminiature products or devices, etc.Examples include, but are not limited to, mechanical parts, medicaldevices and implantable medical devices such as stents, drug deliverydepots, functional structures, microneedle arrays, fibers and rods suchas waveguides, micromechanical devices, microfluidic devices, etc.

In some embodiments, the technology finds use in producing furtherexemplary products including, but not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,catheters, breast implants, testicle implants, pectoral implants, eyeimplants, contact lenses, dental aligners, microfluidics, seals,shrouds, and other applications requiring high biocompatibility;functional structures; microneedle arrays; fibers; rods; waveguides;micromechanical devices; microfluidic devices; fasteners; electronicdevice housings; gears, propellers, and impellers; wheels; mechanicaldevice housings; tools; structural elements; hinges including livinghinges; boat and watercraft hulls and decks; wheels; bottles, jars, andother containers; pipes, liquid tubes, and connectors; foot-ware soles,heels, innersoles, and midsoles; bushings, O-rings, and gaskets; shockabsorbers, funnel/hose assembly, and cushions; electronic devicehousings; shin guards, athletic cups, knee pads, elbow pads, foamliners, padding or inserts, helmets, helmet straps, head gear, shoecleats, gloves, and other wearable or athletic equipment; brushes,combs, rings, jewelry, buttons, snaps, fasteners, watch bands, or watchhousings; mobile phone or tablet casings or housings; computerkeyboards, keyboard buttons, or components; remote control buttons orcomponents; auto dashboard components, buttons, or dials; auto bodyparts, paneling, and other automotive, aircraft or boat parts; cookware,bakeware, kitchen utensils, and steamers; and any number of otherthree-dimensional objects.

Deadzone Control for Three-Dimensional Printing

Layerless or continuous stereolithographic (SLA) three-dimensionalprinting provides significant improvements over traditionallayer-by-layer approaches of forming objects from a polymer. Mostimportantly, continuous printing technologies provide a dramaticimprovement in the achievable print speed. Some conventional continuousthree-dimensional printing technologies achieve improved print speeds bycreating an O₂-inhibited “dead zone” of polymer near the projectionwindow which prevents adhesion of the polymer to the projection windowduring the printing process. See, e.g., U.S. Pat. Nos. 9,205,601 and9,216,546, each of which is incorporated herein by reference. See alsoTumbleston et al. (2015) “Continuous liquid interface production of 3Dobjects” Science 347: 1349, incorporated herein by reference.

However, conventional continuous printing technologies comprising use of“dead zone” inhibition of polymerization are limited by certainperformance characteristics. First, in some of these technologies, thedead zone thickness is strongly dependent on the intensity of thephotoinitiating light. In particular, while high intensity light isfavorable for rapid polymerization and high print speeds, the highintensity also produces a small dead zone thickness that limits printspeeds and the size and shape of printed objects. Therefore, the use ofhigh intensity light reduces or even negates many benefits of continuousprinting methods. Second, the thickness of the dead zone in O₂-inhibitedcontinuous printing technologies is typically approximately 100 μmthick. This narrow dead zone hinders the reflow of uncured resin intothe print area during printing, thus limiting print speeds. Further,liquid reflow into the dead zone depends on the cross-sectional area ofthe item being printed, which further limits the size and shapes ofprinted items. And, oxygen terminates acrylate photo-polymerization,thus increasing materials costs. Accordingly, production of items withlarge cross-sectional areas is severely limited and therefore printingspeeds for such parts are generally very slow. Improvements in thethree-dimensional printing art are needed.

The technology relates, in some embodiments, to producing and/orcontrolling dead zone thickness and/or shape in continuous liquidstereolithogrphy three-dimensional printing. In particular, someembodiments of the technology comprise producing and/or controlling deadzone thickness and/or shape without limiting the intensity of initiatingwavelengths of light. In particular embodiments, the technologycomprises use of a photopolymer system comprising a photoinitiator and aphotoinhibitor having complementary absorbance spectra. For example, insome embodiments polymerization is inhibited by UV light and initiatedby blue light. Using embodiments of the technology, controlling thepenetration depth into the resin bath of the wavelength of light thatactivates the photoinhibitor (e.g., to produce the inhibiting species(e.g., a radical inhibiting species)) enables facile control of the deadzone thickness.

In extant technologies, a dead zone having a small thickness (e.g.,approximately 10 to 100 μm) is produced, e.g., in technologies using O₂as a photoinhibitor. See, e.g., Tumbleston et al. (2015) “Continuousliquid interface production of 3D objects” Science 347: 1349,incorporated herein by reference. The small thickness of the dead zoneseverely limits resin reflow rates into the dead zone, whichconsequently limits print speeds. In particular, small dead zonethickness substantially limits the print speed of items having largecross-sectional areas (e.g., on the order of a few square centimeters).Increasing the dead zone thickness in O₂-inhibited continuous 3Dprinting at a constant initiating intensity has been difficult toachieve; thus, attempts to improve 3D print speeds of regions with largecross sectional areas has failed.

In contrast, the technology provided herein produces a dead zone havinga larger thickness than conventional technologies. For example, in someembodiments, the technology produces a dead zone having a thickness thatis an order of magnitude larger than the dead zone thickness provided byextant technologies (e.g., 100 μm to 1000 μm). That is, in someembodiments the technology provided herein produces a dead zone having athickness of at least approximately 1 mm to 10 mm (e.g., at leastapproximately 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mm). In some embodiments,the technology provided herein produces a dead zone having a thicknessthat is greater than 10 mm. In some embodiments, the increased dead zonethickness minimizes and/or eliminates problems related to resin reflowrates and associated limits on print speed.

Thus, in some embodiments, the technology provides a dead zone forcontinuous three-dimensional printing methods (e.g., continuous liquidinterface production (CLIP) 3D printing) while maintaining highintensity initiating light to improve print speeds of large crosssectional area parts.

In particular, the technology comprises use of a two-wavelength systemin which a first wavelength (e.g., blue light) initiates polymerizationand a second wavelength (e.g., UV) inhibits polymerization. In someembodiments, the technology comprises use of a UV-activatedphoto-inhibitor in a continuous 3D printing technology to create alight-controlled dead zone. Thus, embodiments allow for controlling deadzone thickness, e.g., by adjusting the components of the resincomposition (e.g., comprising polymerizable monomers, photoinitiator,photoinhibitor, and, optionally an absorbing dye (e.g., a UV-absorbingdye)) or the intensity of the inhibiting and initiating light sources(e.g., providing the inhibiting and initiating wavelengths).

Continuous Liquid Interface Printing (CLIP)

The technology relates to providing an improved dead zone for continuousthree-dimensional printing techniques, such as CLIP. In short, CLIP is acontinuous three-dimensional printing process that produces apolymerized item from a composition comprising a liquid photopolymerresin. The composition is held in a reaction chamber comprising a“window” that is transparent to a wavelength of light that initiatespolymerization of the resin. A light source provides a beam of thepolymerizing light through the window, illuminating the composition toinitiate polymerization of the item. The object is lifted slowly up fromthe composition to allow resin to reflow under the item and maintaincontact with the bottom of the item. A “dead zone” lies below theobject, which is a persistent liquid interface that prevents the resinfrom attaching to the window because photopolymerization is inhibited inthe dead zone between the window and the polymerizer. See, e.g., U.S.Pat. Nos. 9,205,601 and 9,216,546; and U.S. Pat. App. Pub. No.2016/0107380, each of which is incorporated herein by reference. Seealso Tumbleston et al. (2015) “Continuous liquid interface production of3D objects” Science 347: 1349 and Int'l Pat. App. No. PCT/US2016/054467(Int'l Pat. Pub. No. WO 2017/059082 A1), each of which is incorporatedherein by reference. The CLIP technology provided improvements overprevious layer-by-layer approaches. For instance, CLIP methods haveprinting speeds that are approximately 100 times faster than thetraditional layer-by-layer methods.

While current CLIP technologies print small cross-sectional area parts(e.g., having cross-sectional areas below 1-3 cm²), technologies basedon O₂-based inhibition strategies are limited in their ability toproduce large-cross sectional area parts rapidly due to the resin reflowlimitations of an oxygen-inhibited dead zone. In particular, extant CLIPmethods have printing speeds up to approximately 1000 mm/hour. Further,some technologies comprise use of an irreversibly photoactivatedphotoinhibitor (e.g., butyl nitrite) (see, e.g., Int'l Pat. App. No.PCT/US2016/054467 (Int'l Pat. Pub. No. WO 2017/059082 A1). Afterphotoactivation, an irreversibly photoactivated photoinhibitor does notrecombine to form an inactive compound by a back reaction and thusinhibits polymerization in the absence of the photoactivating wavelengthand/or can diffuse into regions of the composition where inhibition isnot desired. These limitations severely limit the geometries that areable to be rapidly printed using this technology.

In contrast to extant technologies, embodiments of the technologydescribed herein related to continuous liquid interface productionhaving an increased dead zone size and/or controllable dead zonethickness. In some embodiments, the technology produces items withimproved speed and having cross sectional areas of any size. Inparticular embodiments, the technology provides a method of controllingdead zone thickness through use of a chemical photoinhibitor to inhibitpolymerization; and provides related three-dimensional printing systemsand apparatuses that incorporate this method.

In particular, the technology provides methods for controlling dead zonesize to inhibit free radical polymerization in the region above theprojection window in stereolithographic printing method. In particular,the technology is based on use of a photoactivatable photoinhibitor(e.g., a photoinhibitor that produces a species that inhibitspolymerization of a polymerizable monomer upon irradiation by anappropriate wavelength and intensity of light) and a light source toprovide irradiation by an appropriate wavelength and intensity of light.Using this technology, the shape and/or thickness of the dead zone iscontrolled by the penetration depth of the activating light, which iscontrolled by adjusting the wavelength intensity, adjusting theconcentration of light absorbing substances that attenuate the intensityof the activating wavelength, and/or the adjusting the photoinhibitorconcentration. The technology thus provides control of the thickness ofthe dead zone.

In sum, the technology comprises use of a two-wavelength system forcontinuous 3D printing. A first wavelength (e.g., blue light) initiatesthe polymerization and a second wavelength (e.g., UV) inhibits thepolymerization through the use of a photoinhibitor. Controlling thepenetration depth of the second wavelength into the composition controlsthe depth to which inhibition occurs, thus producing the dead zone.

Compositions for Deadzone Control

The technology relates to compositions for producing a polymer, e.g., toproduce a patterned article of manufacture, e.g., for three-dimensional(3D) printing, etc. In particular, the technology relates to producing apolymer from polymerizable monomers (e.g., from a “resin”). Thetechnology is not limited in the polymerizable monomer used providedthat polymerization of the monomer is initiated by a radical formed fromthe photoinitiator and polymerization of the monomer is inhibited by aradical formed from the photoinhibitor. That is, embodiments providethat polymerization of the monomers occurs where the photoinitiator isactivated by a first wavelength of light and polymerization of themonomers does not occur where the photoinhibitor is activated by asecond wavelength of light.

Accordingly, embodiments relate to compositions comprising a monomer, aphotoinitiator, and a photoinhibitor. In some embodiments, compositionsfurther comprise one or more light absorbing dyes. In some embodiments,compositions further comprise one or more coinitiators. In someembodiments, compositions comprise one or more solvents.

Embodiments of compositions comprise a photoinhibitor. For example, insome embodiments, the technology relates to a composition comprising aphotoinhibitor that is, e.g., a liquid or a gas. In some embodiments,the specific inhibitor depends upon the monomer being polymerized andthe polymerization reaction.

A wide variety of radicals is known which tend to preferentiallyterminate growing polymer radicals, rather than initiatingpolymerizations. For example, ketyl radicals are known in the art toterminate rather than initiate photopolymerizations. Similarly, thetechnology comprises use of a controlled radical polymerization thatuses a radical species to selectively terminate growing radical chains.Examples of terminating radicals that find use in embodiments of thetechnology include, but are not limited to, the sulfanylthiocarbonyl andother radicals generated in photoiniferter polymerizations; thesulfanylthiocarbonyl radicals used in reversible addition-fragmentationchain transfer polymerization; and the nitrosyl radicals used innitroxide mediate polymerization.

In some other embodiments, the technology comprises use of a non-radicalspecies that is generated to terminate growing radical chains, e.g., ametal/ligand complex such as those used as deactivators in atom-transferradical polymerization (ATRP). Therefore, additional non-limitingexamples of a photoinhibitor that finds use in embodiments of thetechnology include thiocarbamates, xanthates, dithiobenzoates,photoinititators that generate ketyl and other radicals that tend toterminate growing polymer chains radicals (e.g., camphorquinone andbenzophenones), ATRP deactivators, and polymeric versions thereof.

In some embodiments, the photoinhibitor is, but not limited to: zincdimethyl dithiocarbamate; zinc diethyl dithiocarbamate; zinc dibutyldithiocarbamate; nickel dibutyl dithiocarbamate; zinc dibenzyldithiocarbamate; tetramethylthiuram disulfide; tetraethylthiuramdisulfide; tetramethylthiuram monosulfide; tetrabenzylthiuram disulfide;tetraisobutylthiuram disulfide; dipentamethylene thiuram hexasulfide;N,N′-dimethyl N,N′-di(4-pyridinyl)thiuram disulfide; 3-Butenyl2-(dodecylthiocarbonothioylthio)-2-methylpropionate;4-Cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid;4-Cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanol; Cyanomethyldodecyl trithiocarbonate; Cyanomethyl[3-(trimethoxysilyl)propyl]trithiocarbonate; 2-Cyano-2-propyl dodecyltrithiocarbonate; S,S-Dibenzyl trithiocarbonate;2-(Dodecylthiocarbonothioylthio)-2-methylpropionic acid;2-(Dodecylthiocarbonothioylthio)-2-methylpropionic acidN-hydroxysuccinimide; Benzyl 1H-pyrrole-1-carbodithioate; Cyanomethyldiphenylcarbamodithioate; Cyanomethyl methyl(phenyl)carbamodithioate;Cyanomethyl methyl(4-pyridyl)carbamodithioate; 2-Cyanopropan-2-ylN-methyl-N-(pyridin-4-yl)carbamodithioate; Methyl2-[methyl(4-pyridinyl)carbamothioylthio]propionate;1-Succinimidyl-4-cyano-4-[N-methyl-N-(4-pyridyl)carbamothioylthio]pentano-ate;Benzyl benzodithioate; Cyanomethyl benzodithioate;4-Cyano-4-(phenylcarbonothioylthio)pentanoic acid;4-Cyano-4-(phenylcarbonothioylthio)pentanoic acid N-succinimidyl ester;2-Cyano-2-propyl benzodithioate; 2-Cyano-2-propyl 4-cyanobenzodithioate;Ethyl 2-(4-methoxyphenylcarbonothioylthio)acetate; 2-Phenyl-2-propylbenzodithioate; Cyanomethyl methyl(4-pyridyl)carbamodithioate;2-Cyanopropan-2-yl N-methyl-N-(pyridin-4-yl)carbamodithioate; or Methyl2-[methyl(4-pyridinyl)carbamothioylthio]propionate.

In some embodiments, the photoinhibitor is used in amounts ranging fromabout 0.01 to about 25 weight percent (wt %) of the composition. In someembodiments, the technology provides a composition comprising aphotoinhibitor at approximately 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18,0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30,0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90,0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0,7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, or 25 wt %.

Embodiments of compositions comprise a photoinhibitor (e.g., aphotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor))). The bridged HABIphotoinhibitor may be one known in the art, as described herein, or asubstituted variation thereof (e.g., comprising one or more moieties(e.g., an alkyl, halogenated alkyl, alkoxyalkyl, alkylamino, cycloalkyl,heterocycloalkyl, polyalkylene, alkoxyl, alkenyl, cycloalkenyl, alkynyl,cycloalkynyl, aryl, heteroaryl, aldehyde, amino, halo, or thio)).

In some embodiments, the photoinhibitor is a HABI compound or a bridgedHABI compound, e.g., as described herein. In some embodiments, thetechnology comprises use of a photoinhibitor, e.g., a “precisephotoinhibitor”, a photoinhibitor having fast back reaction kinetics,and/or a “precise photoinhibitor” having fast back reaction kinetics asdescribed herein and in U.S. Prov. Pat. App. Ser. No. 62/632,834, whichis expressly incorporated herein by reference in its entirety.

In some embodiments, the technology provides a composition comprising aHABI photoinhibitor (e.g., a bridged HABI photoinhibitor) atapproximately 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09,0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21,0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45,0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5,2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5,9.0, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or25 wt %.

In some embodiments, the photoinhibitor is tetraethylthiuram disulfide(TED). TED is an iniferter that inhibits the photopolymerization ofacrylate monomers in the presence of UV light. This occurs by homolyticcleavage of the TED molecule in the presence of ultraviolet light toform two dithiocarbamyl (DTC) radicals. Accordingly, embodimentscomprise TED as a photoinhibitor.

The technology relates to compositions comprising any suitablepolymerizable liquid. In some embodiments, the liquid (also referred toas “resin” herein) comprises monomers, particularly a photopolymerizableand/or free radical polymerizable monomers, and a suitable initiatorsuch as a free radical initiator, and combinations thereof. Examplesinclude, but are not limited to, acrylics, methacrylics, acrylamides,styrenics, olefins, halogenated olefins, cyclic alkenes, maleicanhydride, alkenes, alkynes, carbon monoxide, functionalized oligomers,multifunctional cute site monomers, functionalized PEGs, etc., includingcombinations thereof. In some embodiments, polymerizable monomersinclude, but are not limited to, monomeric, dendritic, and oligomericforms of acrylates, methacrylates, vinyl esters, styrenics, othervinylic species, and mixtures thereof. Examples of liquid resins,monomers, and initiators include, but are not limited to, thosedescribed in U.S. Pat. Nos. 8,232,043; 8,119,214; 7,935,476; 7,767,728;7,649,029; in Int'l Pat. Pub. No. WO 2012129968 A1; in Chinese patentapplication CN 102715751 A; and in Japanese patent application JP2012210408A, each of which is incorporated herein by reference.

In particular, embodiments provide compositions comprising a monomersuch as, e.g., hydroxyethyl methacrylate; n-lauryl acrylate;tetrahydrofurfuryl methacrylate; 2,2,2-trifluoroethyl methacrylate;isobornyl methacrylate; polypropylene glycol monomethacrylates,aliphatic urethane acrylate (e.g., RAHN GENOMER 1122); hydroxyethylacrylate; n-lauryl methacrylate; tetrahydrofurfuryl acrylate;2,2,2-trifluoroethyl acrylate; isobornyl acrylate; polypropylene glycolmonoacrylates; trimethylpropane triacrylate; trimethylpropanetrimethacrylate; pentaerythritol tetraacrylate; pentaerythritoltetraacrylate; triethyleneglycol diacrylate; triethylene glycoldimethacrylate; tetrathyleneglycol diacrylate; tetrathylene glycoldimethacrylate; neopentyldimethacrylate; neopentylacrylate; hexanedioldimethacylate; hexane diol diacrylate; polyethylene glycol 400dimethacrylate; polyethylene glycol 400 diacrylate; diethylglycoldiacrylate; diethylene glycol dimethacrylate; ethyleneglycol diacrylate;ethylene glycol dimethacrylate; ethoxylated bis phenol A dimethacrylate;ethoxylated bis phenol A diacrylate; bisphenol A glycidyl methacrylate;bisphenol A glycidyl acrylate; ditrimethylolpropane tetraacrylate; orditrimethylolpropane tetraacrylate.

Particular embodiments provide compositions comprising an acrylatemonomer, e.g., an acrylate monomer, a methacrylate monomer, etc. In someembodiments, the acrylate monomer is an acrylate monomer such as, butnot limited to, (meth)acrylic acid monomers such as (meth)acrylic acid,methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate,isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate,tert-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate,cyclohexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate,2-ethylhexyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate,dodecyl(meth)acrylate, phenyl(meth)acrylate, toluoyl(meth)acrylate,benzyl(meth)acrylate, 2-methoxyethyl(meth)acrylate,3-methoxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate,2-hydroxypropyl(meth)acrylate, stearyl(meth)acrylate,glycidyl(meth)acrylate, 2-aminoethyl(meth)acrylate,3-(methacryloyloxypropyl)trimethoxysilane, (meth)acrylic acid-ethyleneoxide adducts, trifluoromethylmethyl(meth)acrylate,2-trifluoromethylethyl(meth)acrylate,2-perfluoroethylethyl(meth)acrylate,2-perfluoroethyl-2-perfluorobutylethyl(meth)acrylate,2-perfluoroethyl(meth)acrylate, perfluoromethyl(meth)acrylate,diperfluoromethylmethyl(meth)acrylate,2-perfluoromethyl-2-perfluoroethylethyl(meth)acrylate,2-perfluorohexylethyl(meth)acrylate, 2-perfluorodecylethyl(meth)acrylateand 2-perfluorohexadecylethyl(meth)acrylate.

Some embodiments provide a composition comprising n-butyl acrylate,methyl methacrylate, 2-ethylhexyl acrylate, methyl acrylate, tert-butylacrylate, 2-hydroxyethyl acrylate, glycidyl methacrylate, or acombination thereof. However, embodiments of the technology encompasscompositions comprising any acrylate or (meth)acrylate.

In some embodiments, the technology provides a composition comprising amonomer at approximately 1 to 99.99 wt % (e.g., approximately 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.1, 99.2. 99.3,99.4, 99.5, 99.6, 99.7, 99.8, 99.9, 99.95, to 99.99 wt %).

Embodiments of the technology provide a composition comprising aphotoinitiator. The technology is not limited in the photoinitiatorprovided it is chemically compatible with the photoinhibitor compounds(e.g., a photoinhibitor compound having fast back reaction kinetics(e.g., a HABI photoinhibitor (e.g., a bridged HABI photoinhibitor)))described herein. Further, embodiments relate to use of a photoinitiatorthat is optically compatible with the photoinhibitor compounds describedherein. In particular, the technology comprises use of a photoinitiatorthat is activated by a wavelength of light that is different than thewavelength of light that activates the photoinhibitor.

Accordingly, the technology comprises use of a wide variety ofphotoinitiator compounds and irradiation conditions for activating thephotoinitiator to effect the photoinitiation process. Non-limitingexamples of the photoinitiator include benzophenones, thioxanthones,anthraquinones, camphorquinones, thioxanthones, benzoylformate esters,hydroxyacetophenones, alkylaminoacetophenones, benzil ketals,dialkoxyacetophenones, benzoin ethers, phosphine oxides, acyloximinoesters, alphahaloacetophenones, trichloromethyl-S-triazines,titanocenes, dibenzylidene ketones, ketocoumarins, dye sensitizedphotoinitiation systems, maleimides, and mixtures thereof. Particularexamples of photoinitiators include, e.g.,1-hydroxy-cyclohexyl-phenyl-ketone (IRGACURE 184; BASF, Hawthorne,N.J.); a 1:1 mixture of 1-hydroxy-cyclohexyl-phenyl-ketone andbenzophenone (IRGACURE 500; BASF);2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR 1173; BASF);2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (IRGACURE2959; BASF); methyl benzoylformate (DAROCUR MBF; BASF);oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester;oxy-phenyl-acetic 2-[2-hydroxy-ethoxy]-ethyl ester; a mixture ofoxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester andoxy-phenyl-acetic 2-[2-hydroxy-ethoxy]-ethyl ester (IRGACURE 754; BASF);alpha,alpha-dimethoxy-alpha-phenylacetophenone (IRGACURE 651; BASF);2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)-phenyl]-1-butanone(IRGACURE 369; BASF);2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone(IRGACURE 907; BASF); a 3:7 mixture of2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl) phenyl]-1-butanone andalpha,alpha-dimethoxy-alpha-phenylacetophenone per weight (IRGACURE1300; BASF); diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide (DAROCURTPO; BASF); a 1:1 mixture of diphenyl-(2,4,6-trimethylbenzoyl)-phosphineoxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR 4265; BASF);phenyl bis(2,4,6-trimethyl benzoyl) phosphine oxide, which may be usedin pure form (IRGACURE 819; BASF, Hawthorne, N.J.) or dispersed in water(45% active, IRGACURE 819DW; BASF); 2:8 mixture of phosphine oxide,phenyl bis(2,4,6-trimethyl benzoyl) and2-hydroxy-2-methyl-1-phenyl-1-propanone (IRGACURE 2022; BASF); IRGACURE2100, which comprises phenyl-bis(2,4,6-trimethylbenzoyl)-phosphineoxide); bis-(eta5-2,4-cyclopentadien-1-yl)-bis-[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]-titanium (IRGACURE 784; BASF); (4-methylphenyl)[4-(2-methylpropyl)phenyl]-iodonium hexafluorophosphate (IRGACURE 250;BASF);2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-butan-1-one(IRGACURE 379; BASF);4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone (IRGACURE 2959;BASF); bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide;a mixture of bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphineoxide and 2-hydroxy-2-methyl-1-phenyl-propanone (IRGACURE 1700; BASF);4-Isopropyl-9-thioxanthenone; and mixtures thereof.

In some embodiments, the photoinitiator is used in an amount rangingfrom approximately 0.01 to approximately 25 weight percent (wt %) of thecomposition (e.g., from approximately 0.1 to approximately 3.0 wt % ofthe composition (e.g., approximately 0.2 to 0.5 wt % of thecomposition)). In some embodiments, the technology provides acomposition comprising a photoinitiator at approximately 0.01, 0.02,0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14,0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26,0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70,0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5,5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

Embodiments of the technology provide a composition further comprising acoinitiator, e.g., to enhance the polymerization rate, extent, quality,etc. The technology is not limited in the coinitiator. Non-limitingexamples of co-initiators include primary, secondary, and tertiaryamines; alcohols; and thiols. Particular examples of coinitiatorsinclude, e.g., dimethylaminobenzoate, isoamyl 4-(dimethylamino)benzoate,2-ethylhexyl 4-(dimethylamino)benzoate; ethyl 4-(dimethylamino)benzoate;3-(dimethylamino)propyl acrylate; 2-(dimethylamino)ethyl methacrylate;4-(dimethylamino)benzophenones, 4-(diethylamino)benzophenones;4,4′-bis(diethylamino)benzophenones; methyl diethanolamine;triethylamine; hexane thiol; heptane thiol; octane thiol; nonane thiol;decane thiol; undecane thiol; dodecane thiol; isooctyl3-mercaptopropionate; pentaerythritol tetrakis(3-mercaptopropionate);4,4′-thiobisbenzenethiol; trimethylolpropane tris(3-mercaptopropionate);CN374 (SARTOMER); CN371 (SARTOMER), CN373 (SARTOMER), GENOMER 5142(RAHN); GENOMER 5161 (RAHN); GENOMER 5271 (RAHN); GENOMER 5275 (RAHN),and TEMPIC (BRUNO BOC, Germany).

In some embodiments, the coinitiator is used in an amount ranging fromapproximately 0.0 to approximately 25 weight percent (wt %) of thecomposition (e.g., approximately 0.1 to approximately 3.0 wt % of thecomposition (e.g., 0.1 to 1.0 wt %) when used in embodiments of thecompositions). In some embodiments, the technology provides acomposition comprising a coinitiator at approximately 0, 0.01, 0.02,0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14,0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26,0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70,0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5,5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

Some embodiments comprise use of a photon absorbing component, e.g., alight blocking dye (also known as a “photoabsorber”). In someembodiments, a photon absorbing component is selected in accordance withthe wavelengths of the first and second lights. In some embodiments,dyes are used to both attenuate light and to transfer energy tophotoactive species increasing the sensitivity of the system to a givenwavelength for either or both photoinitiation and photoinhibitionprocesses. In some embodiments, the concentration of the chosen dye ishighly dependent on the light absorption properties of the given dye andranges from approximately 0.001 to approximately 5 weight percent (wt %)of the composition. Useful classes of dyes include compounds commonlyused as UV absorbers for decreasing weathering of coatings including,such as, 2-hydroxyphenyl-benzophenones;2-(2-hydroxyphenyl)-benzotriazoles; and 2-hydroxyphenyl-s-triazines.Other useful dyes include those used for histological staining or dyingof fabrics. A non-limiting list includes Martius yellow, Quinolineyellow, Sudan red, Sudan I, Sudan IV, eosin, eosin Y, neutral red, andacid red. Pigments can also be used to scatter and attenuate light.

In some embodiments, the photon absorbing component (e.g., a lightblocking dye) is used in an amount ranging from approximately 0.0 toapproximately 25 weight percent (wt %) of the composition (e.g.,approximately 0.1 to approximately 3.0 wt % of the composition (e.g.,0.1 to 1.0 wt %) when used in embodiments of the compositions). In someembodiments, the technology provides a composition comprising a photonabsorbing component (e.g., a light blocking dye) at approximately 0,0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12,0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24,0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60,0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5,4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt %.

Some embodiments do not comprise a photon absorbing component (e.g., insome embodiments, compositions are “photoabsorber-free”). In particular,embodiments are provided in which compositions are photoabsorber-free toincrease or maximize the penetration of a wavelength of light through acomposition as described herein (e.g., comprising a polymerizablemonomer, a photoinitiator, and a photoinhibitor).

In some embodiments, a composition further comprises solid particlessuspended or dispersed therein. Any suitable solid particle can be used,depending upon the end product being fabricated. In some embodiments,the solid particles are metallic, organic/polymeric, inorganic, orcomposites or mixtures thereof. In some embodiments, the solid particlesare nonconductive, semi-conductive, or conductive (including metallicand non-metallic or polymer conductors); in some embodiments, the solidparticles are magnetic, ferromagnetic, paramagnetic, or nonmagnetic. Theparticles can be of any suitable shape, including spherical, elliptical,cylindrical, etc.

In some embodiments, a composition comprises a pigment, dye, activecompound, pharmaceutical compound, or detectable compound (e.g.,fluorescent, phosphorescent, radioactive). In some embodiments, acomposition comprises a protein, peptide, nucleic acid (DNA, RNA (e.g.,siRNA)), sugar, small organic compound (e.g., drug and drug-likecompound), etc., including combinations thereof.

In some embodiments, the compositions are homogenous. The technology isrelated to forming polymerized structures; accordingly, in someembodiments, the compositions are heterogeneous because thecompositions, in some embodiments, comprise polymerized andnon-polymerized regions. In some embodiments, compositions of thetechnology comprise a polymer (e.g., comprising polymerized monomers).In some embodiments, a polymerized region is patterned, localized, etc.

In some embodiments, the technology provided herein relates tophotoinhibitors that are activated by light to form a polymerizationinhibiting species and that have a fast back reaction that reforms theinactive photoinhibitor from the polymerization inhibiting species. Insome embodiments, when not activated by light (e.g., in the inactivestate), the photoinhibitors do not inhibit and/or do not retardpolymerization activity and do not have initiating activity; whenactivated by light, the photoinhibitors form an inhibiting species thatinhibits polymerization and that does not initiate polymerization.Accordingly, the technology provided herein relates to photoinhibitionthat is quickly turned “on” and quickly turned “off” by the presence andabsence of light and that does not have undesirable inhibition and/orinitiation activities.

In some embodiments, the photoinhibitor compounds of the technology(e.g., compounds having fast back reaction kinetics and/or HABI (e.g.,bridged HABI compounds)) do not exhibit photoinitiation activity whenirradiated (e.g., when photoactivated) and thus only exhibitphotoinhibition when irradiated (e.g., when photoactivated). Moreover,in some embodiments, the non-photoactivated photoinhibitor compounds ofthe technology do not retard polymerization rates (e.g., by chaintransfer reactions). Finally, in some embodiments, the photoinhibitorcompounds of the technology typically exhibit very weak or zeroabsorbance in the blue region of the electromagnetic spectrum andmoderately absorb in the near-UV region of the electromagnetic spectrum,thus complementing the absorbance spectra of several photoinitiatorsactivated by blue light.

Like HABI compounds, bridged HABI compounds do not exhibitphotoinitiation activity when irradiated. Moreover, bridged HABIcompounds do not participate in chain transfer reactions and thuspolymerization rates are not inherently retarded by the presence of HABIcompounds. Finally, bridged HABI compounds typically exhibit very weakabsorbance in the blue region of the electromagnetic spectrum andmoderately absorb in the near-UV region of the electromagnetic spectrum,thus complementing the absorbance spectrum of several photoinitiatorsactivated by blue light. Finally, bridged HABI compounds exhibit fastback reaction kinetics.

Hexaarylbiimidazole (HABI) Compounds for Deadzone Control

In some embodiments, the technology relates to the use of ahexaarylbiimidazole (HABI) compound as a photoactivated inhibitor ofpolymerization (“photoinhibitor”). Hexaarylbiimidazole (HABI) wasdeveloped in the 1960s as a photochromic molecule by Hayashi and Maeda(see, e.g., Hayashi and Maeda (1960) “Preparation of a new phototropicsubstance” Bull. Chem. Soc. Jpn. 33(4): 565-66, incorporated herein byreference). The recombination “back reaction” is driven by thermalenergy and radical diffusion. The lophyl radical has a large absorptionband in the visible region of the electromagnetic spectrum, whereas HABIabsorbs only in the UV region of the electromagnetic spectrum and istherefore colorless. Consequently, HABI generates a colored radicalspecies upon UV light irradiation and the radicals slowly reform toproduce the colorless HABI imidazole dimer when light irradiation isstopped. Some embodiments comprise use of o-chlorohexaarylbiimidazole(o-Cl-HABI). Irradiation of o-Cl-HABI at the appropriate wavelengthproduces chloro-triphenylimidizolyl radicals, which reform the o-Cl-HABIby a thermally driven back reaction. The halflife of the radicals formedin this reaction is approximately tens of seconds (e.g., approximately10 s). Thus, in some embodiments, the technology relates to ano-chlorohexaarylbiimidazole (o-Cl-HABI) that has a half-life ofapproximately tens of seconds (e.g., approximately 10 s).

Cleavage of the HABI C—N bond by UV irradiation occurs in less than 100fs and is thus nearly (e.g., substantially, effectively) instantaneous;recombination of the radicals to reform HABI is a second order reactionthat occurs over a time of up to a few minutes at room temperature.Thus, the lophyl radicals formed from HABI have a half-life of tens ofseconds to several (e.g., 5 to 10 or more) minutes (see, e.g., Satoh etal. (2007) “Ultrafast laser photolysis study on photodissociationdynamics of a hexaarylbiimidazole derivative” Chem. Phys. Lett. 448(4-6): 228-31; Sathe, et al. (2015) “Re-examining the PhotomediatedDissociation and Recombination Kinetics of Hexaarylbiimidazoles” Ind.Eng. Chem. Res. 54 (16): 4203-12, each of which is incorporated hereinby reference). HABI has been known as a photoinitiator, e.g., forimaging and photoresists. HABI compounds do not initiate on their ownupon formation of radicals. When used as a photoinitiator, the radicalabstracts hydrogen atoms from coinitiator thiol groups (e.g., a crystalviolet precursor) to form an initiating moiety. See, e.g., Dessauer, R.(2006) Photochemistry History and Commercial Applications ofHeaarylbiimidazoles, Elsevier.

In some embodiments, the technology relates to use of a bridged HABI.See, e.g., Iwahori et al. (2007) “Rational design of a new class ofdiffusion-inhibited HABI with fast back-reaction” J Phys Org Chem 20:857-63; Fujita et al. (2008) “Photochromism of a radicaldiffusion-inhibited hexaarylbiimidazole derivative with intensecoloration and fast decoloration performance” Org Lett 10: 3105-08;Kishimoto and Abe (2009) “A fast photochromic molecule that colors onlyunder UV light” J Am Chem Soc 131: 4227-29; Harada et al. (2010)“Remarkable acceleration for back-reaction of a fast photochromicmolecule” J Phys Chem Lett 1: 1112-15; Mutoh et al. (2010) “An efficientstrategy for enhancing the photosensitivity of photochromic[2.2]paracyclophane-bridged imidazole dimers” J Photopolym Sci Technol23: 301-06; Kimoto et al. (2010) “Fast photochromic polymers carrying[2.2]paracyclophane-bridged imidazole dimer” Macromolecules 43: 3764-69;Hatano et al. (2010) “Unprecedented radical-radical reaction of a[2.2]paracyclophane derivative containing an imidazolyl radical moiety”Org Lett 12: 4152-55; Hatano et al. (2011) “Reversible photogenerationof a stable chiral radical-pair from a fast photochromic molecule” JPhys Chem Lett 2: 2680-82; Mutoh and Abe (2011) “Comprehensiveunderstanding of structure-photosensitivity relationships ofphotochromic [2.2]paracyclophane-bridged imidazole dimers” J Phys Chem A115: 4650-56; Takizawa et al. (2011) “Photochromic organogel based on[2.2]paracyclophane-bridged imidazole dimer with tetrapodal ureamoieties” Dyes Pigm 89: 254-59; Mutoh and Abe (2011) “Photochromism of awater-soluble vesicular [2.2]paracyclophane bridged imidazole dimer”Chem Comm 47:8868-70; Yamashita and Abe (2011) “Photochromic propertiesof [2.2]paracyclophane-bridged imidazole dimer with increasedphotosensitivity by introducing pyrenyl moiety” J Phys Chem A 115:13332-37; Kawai et al. (2012) “Entropy-controlled thermal back-reactionof photochromic [2.2]paracyclophane-bridged imidazole dimer” Dyes Pigm92: 872-76; Mutoh et al. (2012) “Spectroelectrochemistry of aphotochromic [2.2]paracyclophane-bridged imidazole dimer: Clarificationof the electrochemical behavior of HABI” J Phys Chem A 116: 6792-97;Mutoh et al. (2013) “Photochromism of a naphthalene-bridged imidazoledimer constrained to the ‘anti’ conformation” Org Lett 15: 2938-41;Shima et al. (2014) “Enhancing the versatility and functionality of fastphotochromic bridged-imidazole dimers by flipping imidazole ring” J AmChem Soc 136: 3796-99; Iwasaki et al. (2014) “A chiral BINOL-bridgedimidazole dimer possessing sub-millisecond fast photochromism” ChemCommun 50: 7481-84; and Yamaguchi et al. (2015) “Nanosecond photochromicmolecular switching of a biphenyl-bridged imidazole dimer revealed bywide range transient absorption spectroscopy” Chem Commun 51: 1375-78,each of which is incorporated herein by reference in its entirety.

Similar to the conventional HABI molecules, the bridged HABI moleculesform radicals instantaneously upon exposure to UV light. However, theradicals are linked by a covalent bond (e.g., one or more covalent bondsand/or, e.g., an R group), which prevents diffusion of the radicals awayfrom one another and thus accelerates the thermally driven reformationof the bridged HABI molecule. Accordingly, the bridged HABI moleculesinstantaneously produce radicals upon UV light irradiation and theradicals rapidly disappear when UV irradiation is stopped.

As used herein, the term “bridged HABI” refers to a HABI molecule inwhich the triphenylimidazolyl radicals are linked (e.g., by one or morecovalent bonds or by an R group) to each other such that they do notdiffuse away from one another upon hemolytic cleavage of the bondconnecting the imidazole centers (e.g., by light). As used herein, theterm “X-bridged HABI”, where “X” refers to an R group (e.g., moiety,chemical group, etc.), refers to a HABI wherein the imidazolyl moietiesare linked by the R group.

In an exemplary embodiment, the half-life of the radicals formed from anaphthalene-bridged HABI and a [2.2]paracyclophane-bridged HABI dimerare approximately 830 ms and 33 ms at 25° C. in benzene, respectively.See, e.g., Iwahori et al. (2007) “Rational design of a new class ofdiffusion-inhibited HABI with fast back-reaction” J Phys Org Chem 20:857-63; Fujita et al. (2008) “Photochromism of a radicaldiffusion-inhibited hexaarylbiimidazole derivative with intensecoloration and fast decoloration performance” Org Lett 10: 3105-08;Kishimoto and Abe (2009) “A fast photochromic molecule that colors onlyunder UV light” J Am Chem Soc 131: 4227-29, each of which isincorporated herein in its entirety.

Additional exemplary embodiments relate to use of a HABI in which theimidazole moieties are linked by a 1,1′-bi-naphthol bridge. The1,1′-bi-naphthol-bridged HABI has a half-life of approximately 100 μs.See, e.g., Iwasaki et al. (2014) “A chiral BINOL-bridged imidazole dimerpossessing sub-millisecond fast photochromism” Chem Commun 50: 7481-84,incorporated herein by reference. In some embodiments, the technologyrelates to use of a HABI comprising a bond linking the imidazolyl groups(e.g., a bond links the imidazolyl groups) that has a half-life ofapproximately 100 ns, which is the fastest thermal back reaction for aHABI compound presently known in the art. See, e.g., Yamaguchi et al.(2015) “Nanosecond photochromic molecular switching of abiphenyl-bridged imidazole dimer revealed by wide range transientabsorption spectroscopy” Chem Commun 51: 1375-78, incorporated herein byreference in its entirety.

The bridged HABI photoinhibitor may be one known in the art, asdescribed herein, or a substituted variation thereof (e.g., comprisingone or more moieties (e.g., an alkyl, halogenated alkyl, alkoxyalkyl,alkylamino, cycloalkyl, heterocycloalkyl, polyalkylene, alkoxyl,alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl,aldehyde, amino, halo, or thio) on one or more phenyl rings and/or onthe R group).

Accordingly, the technology relates in some embodiments to use ofbridged HABI molecules as photoactivatable inhibitors of polymerization.In some embodiments, the bridged HABI molecules form a radical uponirradiation by light (e.g., at an appropriate wavelength to form aradical from the HABI). In some embodiments, the radical rapidlydisappears upon stopping the irradiation by light. For example,embodiments relate to a bridged HABI that forms a radical having ahalf-life of approximately 100 ns to 100 μs to 100 ms to 100 s (e.g.,10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700,800, 900, or 1000 ns; 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300,400, 500, 600, 700, 800, 900, or 1000 μs; 10, 20, 30, 40, 50, 60, 70,80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ms; or 0,20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800,900, or 1000 s). That is, after formation of the radical by irradiationof the bridged HABI at the appropriate wavelength, the radical rapidlyreforms the bridged HABI upon stopping the irradiation. Consequently,the radical is only formed in the region irradiated by the appropriatewavelength to form a radical from the HABI.

Technologies (e.g., methods, systems, kits, apparatuses, uses, andcompositions) related to use of HABI compounds and bridged HABIcompounds are described herein and in U.S. Prov. Pat. App. Ser. No.62/632,834, which is expressly incorporated herein by reference in itsentirety.

Irradiation for Deadzone Control

Embodiments relate to irradiating polymerizable compositions (e.g.,comprising a polymerizable monomer, a photoinitiator, and aphotoinhibitor) with multiple wavelengths of light The Beer-Lambert Lawdescribes the variation in intensity of an incident light beam as itpasses through an absorbing medium:

$\begin{matrix}{\frac{\phi_{l}}{\phi_{0}} = {10^{{- \epsilon_{i}}c_{i}l}}} & (1)\end{matrix}$Where ϕ_(l) is the photon flux at a depth l into the medium, ϵ_(i) isthe molar absorption coefficient, c_(i) is the concentration of theabsorbing species, and ϕ₀ is the incident photon flux. It is possible toindependently control the intensity of different wavelengths of light byvarying their absorbance within a medium. This is commonly done in 3Dprinting by the addition of a light absorbing compound (e.g., a lightabsorbing dye) into photopolymer resin.

According to embodiments of the technology, a two-wavelength system isused to produce a dead zone and produce an item comprising a polymer. Insome embodiments, a first wavelength initiates polymerization (e.g.,blue light) and a second wavelength inhibits polymerization (e.g., UVlight). As shown previously, independently controlling the intensitiesof the first and second wavelengths lights within a polymer resin bathprovides for manipulating the ratio of the initiating, I_(I), andinhibiting, I_(IN), intensities. See, e.g., FIG. 24.

The polymerization rate in the presence of a photoinhibiting speciesscales according to the equation:(I _(I) −βλI _(IN))^(0.5)  (2)in which ß is a constant encompassing the ratios of the inhibitor to theinitiator absorption cross sections, quantum yields, and reaction rateconstants.

Therefore, as the I_(I)/I_(IN) ratio increases, the polymerization rateincreases; thus, polymerization will occur more rapidly in the regionaway from the projection window. Thus, embodiments comprise producing adead zone region at the window where polymerization is minimized,inhibited, prevented, terminated, and/or eliminated. In someembodiments, the thickness of the dead zone is modified by eitheradjusting the intensities of the incident lights or by modifying thecomposition of the polymer mixture to tune the absorbance. Thistechnology provides the ability to modify the dead zone thickness whilemaintaining high curing light intensities.

In some embodiments, a first wavelength produces initiating radicalsfrom the photoinitiator and a second wavelength produces inhibitingradicals from a photoinhibitor. During irradiation, regions (e.g.,volumes, areas, etc.) of the composition are exposed to: 1) the firstwavelength only; 2) the second wavelength only; or 3) both the first andsecond wavelengths. Accordingly, polymerization occurs in regionsirradiated by the first wavelength only (e.g., in regions irradiated bythe first wavelength but not irradiated by the second wavelength). And,polymerization is inhibited in regions irradiated by the secondwavelength (e.g., in regions irradiated by the second wavelength and thefirst wavelength; and in regions irradiated by the second wavelength butnot irradiated by the first wavelength). Thus, by providing control ofthe wavelength, intensity, pattern (e.g., cross sectional area, crosssection shape, etc.), and direction of the first and/or secondwavelengths of light (e.g., as provided by one or more sources), thetechnology provides control over the polymerized region in thecomposition. In some embodiments, wavelength, intensity, pattern (e.g.,cross sectional area, cross section shape, etc.), and direction of thefirst and/or second wavelengths of light (e.g., as provided by one ormore sources) is controlled (e.g., varies) as a function of time.

For instance, FIGS. 25A and 25B shows a schematic diagram exemplifyingan embodiment of the technology described herein. In FIG. 25A, an item101 is being produced from a resin composition 102 (e.g., comprising apolymerizable monomer, a photoinitiator, and a photoinhibitor) accordingto an embodiment of the technology provided herein. A build supportplate 103 is attached to the item 101 and draws it up from the resincomposition 102. A first wavelength of light 104 (dotted lines) and asecond wavelength of light 105 (solid lines) irradiate the resincomposition 102 through an optically transparent window 106. The firstwavelength of light 104 has a wavelength and intensity to activate thephotoinhibitor (e.g., to produce an inhibiting species (e.g., aninhibiting radical) in the composition. The second wavelength of light105 has a wavelength and intensity to activate the photoinitiator (e.g.,to produce an initiating species (e.g., an initiating radical) in thecomposition. The first wavelength of light 104 activates thephotoinhibitor to produce the dead zone 107 as shown in FIG. 25B.

FIG. 25B shows a schematic enlargement of a region of the schematicshown in FIG. 25A. The plot at the left shows the intensity of theinitiating wavelength (solid line), the intensity of the inhibitingwavelength (dashed line), and the polymerization reaction rate (dot-dashline) within the composition 102 shown at the right as a function ofdistance from the optically transparent window 106. The vertical axisshows distance (in arbitrary units appropriate to scale for a CLIP-typeapparatus) from the optically transparent window 106 up through theresin composition 102 in the direction of the build support plate 103.The origin of the vertical axis is at the outside surface of theoptically transparent window 106 upon which the first wavelength oflight 104 (dotted lines) and second wavelength of light 105 (solidlines) impinge prior to passing through the optically transparent window106 to irradiate the resin composition 102. The horizontal axis showsthe intensities of the initiating wavelength (solid line) and theinhibiting wavelength (dashed line) with the origin at zero (0). Theintensities of the initiating and inhibiting wavelengths are highestprior to and when passing through the optically transparent window 106and decrease to zero as the initiating and inhibiting wavelengths passthrough the resin composition 102. The horizontal axis also shows therelative polymerization reaction rate (dash-dot line) producing thepolymer with the origin at (zero). The dead zone 107 is the region wherephotoinhibition occurs within the resin composition such that thepolymerizable monomers do not polymerize. Above the dead zone 107,polymerization occurs where inhibition does not inhibit polymerizationand the initiating intensity is sufficient to activate thephotoinitiator (e.g., to produce an initiating species (e.g., aninitiating radical)).

In some embodiments, the resin composition 102 comprises a polymerizablemonomer (e.g., a di(meth)acrylate monomer), a photoinitiator (e.g.,camphorquinone), and a photoinhibitor. In some embodiments, thecompositions comprise a photoabsorber. In some embodiments, thecompositions do not comprise a photoabsorber (e.g., in some embodiments,the composition is photoabsorber-free).

In some embodiments, the resin composition 102 is irradiated by anear-UV light 104 (e.g., approximately 364 nm) to activate thephotoinhibitor in the resin composition 102. In some embodiments, thenear-UV light 104 is provided as a pattern to produce a region withinthe resin composition 102 having a particular shape that comprises thephotoinhibitor. In some embodiments, the pattern is provided by apattern component such as a mask. In some embodiments, the near-UV light104 passes through a mask or other component to provide the near-UVlight in a pattern that irradiates the composition to produce theinhibiting moiety (e.g., the inhibiting radical).

Simultaneously, in some embodiments, the resin composition 102 isirradiated by a blue light 105 (e.g., approximately 470 nm) to activatethe photoinitiator in the resin composition 102. In some embodiments,the blue light 107 is provided as a pattern to produce a region withinthe composition having a particular shape that comprises thephotoinitiator. In some embodiments, the pattern is provided by apattern component such as a mask. In some embodiments, the blue lightpasses through a mask or other component to provide the blue light in apattern that irradiates the composition to produce the initiating moiety(e.g., the initiating radical).

While FIGS. 25A and 25B depict an illustrative embodiment of thetechnology, the technology is not limited to the features and aspectsshown therein or discussed herein in reference to FIGS. 25A and 25B.

For instance, the technology is not limited in the light used forirradiation and/or the light sources that are used for irradiation,e.g., a light having a first wavelength and a light having a secondwavelength. The technology is not limited in the cross sectional shapes,areas, and/or patterns of the first and/or second wavelengths or theintensities of the first and/or second wavelengths. The technology isnot limited in the wavelengths of the first and/or second sources.

As noted herein, the technology is not limited in the source of thelight (e.g., one or more sources of one or more wavelengths of light).Accordingly, embodiments of the technology comprise, and comprise useof, a suitable light source (or combination of light sources) selectedto be appropriate for the particular monomer (“resin”), photoinitiator,and/or photoinhibitor employed. While embodiments are discussed in termsof a light source, embodiments also include sources of radiationincluding an electron beam and other ionizing radiation sources.

In some embodiments, the light source is an actinic radiation source,such as one or more light sources (e.g., one or more light sourcesproviding visible and/or ultraviolet electromagnetic radiation). In someembodiments, a light source is, e.g., an incandescent light, fluorescentlight, phosphorescent or luminescent light, laser, light-emitting diode,etc., including arrays thereof. In some embodiments, a light sourceprovides even coverage of light. Accordingly, in some embodiments alight source is a collimated beam or a planar waveguide, e.g., toprovide even coverage of a light.

In some embodiments, the first wavelength is produced by a first lightsource, and the second wavelength is produced by a second light source.In some embodiments, the first wavelength and the second wavelength areproduced by the same light source. In some embodiments, the firstwavelength and second wavelength have emission peak wavelengths that areat least 5 or 10 nm apart from one another (e.g., the emission peak ofthe first wavelength is at least 5, 6, 7, 8, 9, 10, or more nm apartfrom the emission peak of the second wavelength).

In particular, as discussed herein, the technology relates to use of afirst wavelength to activate a photoinitiator. Activating thephotoinitiator produces an initiating moiety (e.g., initiating radicals)from the photoinitiator. The initiating radicals initiate polymerizationof the polymerizable monomers. Further, as discussed herein, thetechnology relates to use of a second wavelength to activate aphotoinhibitor. Activating the photoinhibitor produces an inhibitingmoiety (e.g., inhibiting radicals) from the photoinhibitor. Theinhibiting radicals prevent polymerization of the polymerizablemonomers. Accordingly, embodiments of the technology relate to use of 1)a first wavelength of light that activates the photoinitiator and thatdoes not activate the photoinhibitor; and 2) a second wavelength oflight that activates the photoinitiator and that does not activate thephotoinhibitor. Thus, the photoinhibitor, photoinitiator, firstwavelength, and second wavelength are chosen such that: 1) the firstwavelength of light activates the photoinitiator and does not activatethe photoinhibitor; and 2) the second wavelength of light activates thephotoinhibitor and does not activate the photoinhibitor.

In some embodiments, the first wavelength is at or near the peak of theabsorbance spectrum of the photoinitiator, e.g., within 50 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) of thepeak of the absorbance spectrum of the photoinitiator. In someembodiments, the second wavelength is at or near the peak of theabsorbance spectrum of the photoinhibitor, e.g., within 50 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) of thepeak of the absorbance spectrum of the photoinhibitor.

A wavelength of light that is not strongly absorbed penetrates moredeeply into a composition comprising an absorbing compound (e.g., aphotoinitiator or photoinhibitor) and therefore activates a largervolume of photoactivated compound (e.g., a photoinitiator orphotoinhibitor). Accordingly, in some embodiments, the first wavelengthis chosen to be a wavelength that activates the photoinitiator, but thatis also not strongly absorbed by the photoinitiator; similarly, in someembodiments, the second wavelength is chosen to be a wavelength thatactivates the photoinhibitor, but that is also not strongly absorbed bythe photoinhibitor.

In some embodiments, the first wavelength is not near the peak of theabsorbance spectrum of the photoinitiator, e.g., at least 50 nm (e.g.,at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) away fromthe peak of the absorbance spectrum of the photoinitiator. In someembodiments, the second wavelength is not near the peak of theabsorbance spectrum of the photoinhibitor, e.g., at least 50 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nm) away fromthe peak of the absorbance spectrum of the photoinhibitor. Similarly, insome embodiments, the absorbance of the photoinitiator at the firstwavelength is less than 25% (e.g., less than 25, 24, 23, 22, 21, 20, 19,18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4.5, 4, 3.5, 3, 2.5,2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6,0.5, 0.4, 0.3, 0.2, 0.1, or 0.05%) of the absorbance of thephotoinitiator at the wavelength of the absorbance peak of thephotoinitiator. And, in some embodiments, the absorbance of thephotoinhibitor at the second wavelength is less than 25% (e.g., lessthan 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9,8, 7, 6, 5, 4.5, 4, 3.5, 3, 2.5, 2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3,1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, or 0.05%) ofthe absorbance of the photoinhibitor at the wavelength of the absorbancepeak of the photoinhibitor.

In some embodiments, light is provided in a pattern. In someembodiments, the first wavelength of light is provided as a pattern. Insome embodiments, the second wavelength of light is provided as apattern. The first and second wavelengths may be provided in patternsthat are the same or different. In some embodiments, the methodscomprise irradiating a composition as described herein with a pattern ofa first wavelength of light. In some embodiments, the methods compriseirradiating a composition as described herein with a pattern of a secondwavelength of light. In some embodiments, different patterns of lightfor two different wavelengths of light are used. In some embodiments,the patterns overlap in different configurations. In some embodiments,the methods comprise irradiating a composition as described herein witha first pattern of a first wavelength of light. In some embodiments, themethods comprise irradiating a composition as described herein with asecond pattern of a second wavelength of light.

In some embodiments, the technology provides a pattern having aresolution with millions of pixel elements. In some embodiments, thetechnology provides a pattern having millions of pixel elements whosewavelength and/or intensities are varied to change the pattern ofirradiation provided to the composition. For example, in someembodiments the pattern is provided by a DLP comprising more than 1,000(e.g., more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50thousand or more) rows and/or more than 1,000 (e.g., more than 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 thousand or more) columns. Insome embodiments the pattern is provided by a LCD comprising more than1,000 (e.g., more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or50 thousand or more) rows and/or more than 1,000 (e.g., more than 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 thousand or more) columns.

In some embodiments, a light source is a liquid crystal display (LCD),light emitting diode (LED), or a digital light projector (DLP), e.g., todeliver a pattern of light. In some embodiments, the light sourceincludes a pattern-forming element operatively associated with acontroller. In some embodiments, the light source or pattern formingelement comprises a digital (or deformable) micromirror device (DMD)with digital light processing (DLP), a spatial modulator (SLM), or amicroelectromechanical system (MEMS) mirror array, a mask (aka areticle), a silhouette, or a combination thereof. See, U.S. Pat. No.7,902,526, incorporated herein by reference. In some embodiments, thelight source comprises a spatial light modulation array such as a liquidcrystal light valve array or micromirror array or DMD (e.g., with anoperatively associated digital light processor, typically under thecontrol of a suitable controller), configured to carry out exposure orirradiation of a composition as described herein (e.g., by masklessphotolithography). See, e.g., U.S. Pat. Nos. 6,312,134; 6,248,509;6,238,852; and 5,691,541, each of which is incorporated herein byreference.

In some embodiments, the technology provides a pattern having aresolution with millions of pixel elements. In some embodiments, thetechnology provides a pattern having millions of pixel elements whosewavelength and/or intensities are varied to change the pattern ofirradiation provided to the composition.

For example, in some embodiments the technology relates to controllingthe intensity of a light source at pixel resolution (e.g., a firstsource providing a first wavelength to activate the photoinitiatorand/or a second source providing a second wavelength to activate thephotoinhibitor). Providing a light source with intensities varying atthe pixel level provides, in some embodiments, a three-dimensionalcontour of light intensity at the first and/or second wavelength(s) thatirradiates the composition comprising the polymerizable monomer, thephotoinhibitor, and the photoinitiator. In some embodiments, theintensity at light is controlled at the pixel level and varies as afunction of time at the pixel level.

For example, in some embodiments the pattern is provided by a DLPcomprising more than 1,000 (e.g., more than 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,46, 47, 48, 49, or 50 thousand or more) rows and/or more than 1,000(e.g., more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50thousand or more) columns. In some embodiments the pattern is providedby a LCD comprising more than 1,000 (e.g., more than 1, 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,44, 45, 46, 47, 48, 49, or 50 thousand or more) rows and/or more than1,000 (e.g., more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or50 thousand or more) columns.

The technology is not limited in the pattern of irradiation produced bya first and/or second light source. For example, in some embodiments,the pattern comprises one or more geometric shapes, one or moreirregular shapes, or one or more lines, dots, or other graphic features.In some embodiments, the pattern of irradiation changes with time, e.g.,in some embodiments the pattern of irradiation is provided as a seriesof patterned images, e.g., a movie.

For example, in some embodiments, the technology comprises use ofirradiation provided as a time-variable pattern of the first and/orsecond wavelength. In some embodiments, the length of time that eachpattern of irradiation is provided depends on, e.g., the wavelengthand/or intensity of the wavelength, the presence or absence of a photonabsorbing substance (e.g., a dye) in the composition, the photoinitiatorused, the photoinhibitor used (e.g., a photoinhibitor compound havingfast back reaction kinetics (e.g., a HABI photoinhibitor (e.g., abridged HABI photoinhibitor)))), and the volume of the composition(e.g., the dimensions of the composition (e.g., in the direction inwhich the light is travelling)). In some embodiments, a composition isirradiated by a pattern for a time that is approximately 1 ps to 6,000seconds or more (e.g., approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5,or 1 ns; approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 μs;approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 ms; approximately0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 s; or approximately 0.001,0.005, 0.01, 0.05, 0.1, 0.5, or 1 μs; approximately 0.001, 0.005, 0.01,0.05, 0.1, 0.5, or 1 minute).

In some embodiments, a “dark” period is provided between eachirradiation pattern. That is, in some embodiments, the composition isnot irradiated for a period of time between the time periods ofirradiation by the first and/or second wavelength. In some embodiments,the period of time during which the composition is not irradiatedbetween periods of irradiation is approximately 1 ns to 6,000 seconds ormore (e.g., approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 ns;approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 μs; approximately0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or 1 ms; approximately 0.001, 0.005,0.01, 0.05, 0.1, 0.5, or 1 s; or approximately 0.001, 0.005, 0.01, 0.05,0.1, 0.5, or 1 μs; approximately 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, or1 minute). In some embodiments, the period of time during which thecomposition is not irradiated between periods of irradiation isapproximately 0.1 ps to 1 second (e.g., approximately 0.001, 0.002,0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04,0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9 or 1 ps; approximately 0.001, 0.002, 0.003, 0.004, 0.005, 0.006,0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08,0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 ns; approximately0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9 or 1 μs; or approximately 0.001, 0.002, 0.003, 0.004,0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 s).Thus, in some embodiments, the pattern varies tens, hundreds, thousands,or millions of times to produce a polymerized article within thecomposition.

The technology is not limited in the intensity of the first and/orsecond wavelengths provided by the first and/or second sources (e.g.,that are emitted from the first and/or second sources and/or thatimpinge on the outside surface of the optically transparent window 106).For example, embodiments comprise light provided at intensities of from0.001 to 1000 mW/cm² (e.g., approximately 0.001, 0.005, 0.01, 0.05, 0.1,0.5, 1, 5, 10, 50, 100, 500, or 1000 mW/cm²). In some embodiments, lightis provided having a wavelength in the UV, visible, and/or infraredregions of the electromagnetic spectrum (e.g., wavelengths of 10 nm to 1mm (e.g., 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 105, 110, 115, 120,125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190,195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260,265, 270, 275, 280, 285, 290, 295, 300, 305, 310, 315, 320, 325, 330,335, 340, 345, 350, 355, 360, 365, 370, 375, 380, 385, 390, 395, 400,405, 410, 415, 420, 425, 430, 435, 440, 445, 450, 455, 460, 465, 470,475, 480, 490, 495, 500, 505, 510, 515, 520, 525, 530, 535, 540, 545,550, 555, 560, 565, 570, 575, 580, 585, 590, 595, 600, 605, 610, 615,620, 625, 630, 635, 640, 645, 650, 655, 660, 665, 670, 675, 680, 685,690, 695, 700, 705, 710, 715, 720, 725, 730, 735, 740, 745, 750, 755,760, 765, 770, 775, 780, 785, 790, 795, 800, 805, 810, 815, 820, 825,830, 835, 840, 845, 850, 855, 860, 865, 870, 875, 880, 885, 890, 895,900, 905, 910, 915, 920, 925, 930, 935, 940, 945, 950, 955, 960, 965,970, 975, 980, 985, 990, 995, or 1000 nm)).

The technology is not limited in the cross sectional area of the beamand/or two-dimensional pattern that is provided (e.g., the beam orpattern of the first and/or second wavelengths of light provided by thefirst and/or second sources). For example, in some embodiments the crosssectional area of the beam and/or two-dimensional pattern of the firstand/or second wavelength is approximately 0.5 μm² to 10,000 mm² (e.g.,approximately 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800,900, or 1000 μm²; approximately 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500,600, 700, 800, 900, or 1000 mm²; or approximately 0.5, 0.6, 0.7, 0.8,0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100,200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000,6000, 7000, 8000, 9000, or 10,000 mm²). In some embodiments, the crosssectional area of the beam and/or two-dimensional pattern that isprovided (e.g., the beam or pattern of the first and/or secondwavelengths of light provided by the first and/or second sources) isvaried (e.g., increased, decreased) with time.

In some embodiments, irradiation as described herein finds use inmethods of producing an item comprising a polymer, e.g., by thepolymerization of polymerizable monomers. Thus, in some embodiments thetechnology comprises irradiating a composition, e.g., with a firstand/or a second wavelength, e.g., as provided by a first and/or a secondwavelength of light. Embodiments of methods comprising irradiating stepsare described herein. Technologies (e.g., methods, systems, apparatuses,kits, and compositions) related to use of two-color irradiation andphotoinhibitor/photoinitiator combinations are described herein and inU.S. Prov. Pat. App. Ser. No. 62/632,903, which is expresslyincorporated herein by reference in its entirety.

Uses for Deadzone Control

The technology is not limited in its use and finds use in a wide varietyof polymer-associated technologies. In some embodiments, thecompositions, methods, and systems described herein are particularlyuseful for making three-dimensional articles. For instance, thetechnology described herein (e.g., photoinhibitor compounds having fastback reaction kinetics (e.g., a HABI photoinhibitor (e.g., a bridgedHABI photoinhibitor))) find use in three-dimensional printing (e.g.,ultra-rapid 3D printing). Three dimensional (3D) printing or additivemanufacturing is a process in which a 3D digital model is manufacturedby the accretion of construction material. In some embodiments, a 3Dprinted object is created by utilizing computer-aided design (CAD) dataof an object through sequential construction of two dimensional (2D)layers or slices that correspond to cross-sections of 3D objects.

In some embodiments, the technology finds use in continuous layerinterface production (CLIP). In particular, in some embodiments, thephotoinhibitor compound having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)) finds use inproducing a dead zone in CLIP. See, e.g., U.S. Pat. Nos. 9,205,601;9,216,546; and U.S. Pat. App. Pub. No. 2016/0067921, each of which isincorporated herein by reference. In particular, the photoinhibitorcompounds having fast back reaction kinetics (e.g., a HABIphotoinhibitor (e.g., a bridged HABI photoinhibitor)) andphotoinitiator/photoinhibitor technology provided herein finds use inthe three-dimensional printing technology described in U.S. Pat. App.Pub. No. 2016/0067921 with the TED being replaced by the bridged HABIphotoinhibitors described herein.

In some embodiments, the technology finds use in stereolithography (SL).SL is one type of additive manufacturing where a liquid resin ishardened by selective exposure to a radiation to form each 2D layer. Insome embodiments, the radiation is in the form of electromagnetic waves(e.g., light, photons) or an electron beam. The most commonly appliedenergy source is ultraviolet, visible, or infrared radiation. The liquidphotopolymer resin can contain monomers, oligomers, fillers andadditives such as photoinitiators, blockers, colorants and other typesdepending on the targeted properties of the resin.

In some embodiments, the technology finds use in true additivemanufacturing and/or in direct write lithography. Products that may beproduced by the compositions, methods, and systems described hereininclude, but are not limited to, large-scale models or prototypes, smallcustom products, miniature or microminiature products or devices, etc.Examples include, but are not limited to, mechanical parts, medicaldevices and implantable medical devices such as stents, drug deliverydepots, functional structures, microneedle arrays, fibers and rods suchas waveguides, micromechanical devices, microfluidic devices, etc.

In some embodiments, the technology finds use in producing furtherexemplary products including, but not limited to, medical devices andimplantable medical devices such as stents, drug delivery depots,catheters, breast implants, testicle implants, pectoral implants, eyeimplants, contact lenses, dental aligners, microfluidics, seals,shrouds, and other applications requiring high biocompatibility;functional structures; microneedle arrays; fibers; rods; waveguides;micromechanical devices; microfluidic devices; fasteners; electronicdevice housings; gears, propellers, and impellers; wheels; mechanicaldevice housings; tools; structural elements; hinges including livinghinges; boat and watercraft hulls and decks; wheels; bottles, jars, andother containers; pipes, liquid tubes, and connectors; foot-ware soles,heels, innersoles, and midsoles; bushings, w-rings, and gaskets; shockabsorbers, funnel/hose assembly, and cushions; electronic devicehousings; shin guards, athletic cups, knee pads, elbow pads, foamliners, padding or inserts, helmets, helmet straps, head gear, shoecleats, gloves, and other wearable or athletic equipment; brushes,combs, rings, jewelry, buttons, snaps, fasteners, watch bands, or watchhousings; mobile phone or tablet casings or housings; computerkeyboards, keyboard buttons, or components; remote control buttons orcomponents; auto dashboard components, buttons, or dials; auto bodyparts, paneling, and other automotive, aircraft or boat parts; cookware,bakeware, kitchen utensils, and steamers; and any number of otherthree-dimensional objects.

EXAMPLES

Contemporary, layer-wise additive manufacturing approaches affordsluggish object fabrication rates and often yield parts with ridgedsurfaces; in contrast, continuous stereolithographic printing overcomesthe layer-wise operation of conventional devices, greatly increasingachievable print speeds and generating objects with smooth surfaces.During the development of embodiments of the technology provided herein,experiments were conducted to test methods for rapid and continuousstereolithographic additive manufacturing by employing two-colorirradiation of (meth)acrylate resin formulations containingcomplementary photo-initiator and photo-inhibitor species. In thisapproach, photopatterned polymerization inhibition volumes generated byirradiation at one wavelength spatially confine the regionphotopolymerized by a second, concurrent irradiation wavelength.Moreover, the inhibition volumes created using this method enablelocalized control of the polymerized region thickness to effectsingle-exposure, far-side topographical patterning.

Materials and Methods

Triethylene glycol dimethacrylate (TEGDMA, Esstech Inc., Essington, Pa.,USA) and bisphenol A glycidyl methacrylate (bisGMA, Esstech) wereformulated as a mixture consisting of 50 wt % TEGDMA and 50 wt % bisGMA.N-(npropyl) maleimide (NPM, Alfa Aesar, Haverhill, Mass., USA) andtriethylene glycol divinyl ether (TEGDVE, Sigma-Aldrich, St. Louis, Mo.,USA) were formulated as a mixture such that the maleimide and vinylether functional groups were present at a 1:1 stoichiometric ratio.Bisphenol A ethoxylate diacrylate, EO/phenol 4.0 (BPAEDA, Sigma-Aldrich)was used without comonomers. (±)-Camphorquinone (CQ, Esstech) was usedas a blue light-active photoinitiator in conjunction withethyl-4-dimethylaminobenzoate (EDAB, Esstech) as a co-initiator at theconcentrations indicated.2,2′-Bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole(o-Cl-HABI, TCI America, Portland, Oreg., USA) was used as aphotoinhibitor at the concentrations indicated. Owing to poor solubilityof o-Cl-HABI in the monomers, o-Cl-HABI was dissolved in tetrahydrofuran(THF, containing 0.025% butylated hydroxytoluene as preservative, FisherScientific, Hampton, N.H., USA) as a ˜30 wt % solution prior toformulating the resins. 2-Mercaptobenzothiazole (MBT, Sigma-Aldrich) wasused as a co-initiator in conjunction with o-Cl-HABI.

The bisGMA/TEGDMA monomer mixture was formulated with 0.2 wt % CQ, 0.5wt % EDAB, and 3 wt % o-Cl-HABI. BPAEDA was formulated with 0.2 wt % CQ,0.5 wt % EDAB, and 2 wt % o-Cl-HABI. The TEGDVE/NPM monomer mixture wasformulated with 1.0 wt % CQ, 0.5 wt % EDAB, and 5 wt % o-Cl-HABI. Allmonomer quantities were adjusted to account for the THF in whicho-Cl-HABI was dissolved.

For the o-Cl-HABI photoinitiation testing, bisGMA/TEGDMA was formulatedwith 1 wt % o-Cl-HABI and either no co-initiator or 0.5 wt % of eitherEDAB or MBT.

Photopolymerizable resins was prepared with a 1/0.5/3 wt % mixture ofCQ, EDAB, and o-Cl-HABI, respectively. Inhibition volume thickness testswere conducted with exclusively trimethylolpropane triacrylate (TMPTA,Alfa Aesar) as monomer. Resins used for continuous 3D printing andvarying intensity printing were mixtures of monomers, oligomers andreactive diluents. Monomers used were TMPTA, TEGDMA, 1,6-hexandioldiacrylate (HDDA, TCI America, Portland, Oreg., USA). Sartomer CN2920(Sartomer, Exton, Pa., USA) and Sartomer CN981 (Sartomer) were theoligomers used. Isobornyl acrylate (TCI America) was used as a reactivediluent. Tinuvin 328 (BASF, Florham Park, N.J., USA) was used as a UVabsorber and Epolight 5675 (Epolin, Newark, N.J., USA) was used as theblue light absorber. All chemicals were used as received. Allpolymerizations were conducted at room temperature.

UV-visible spectrophotometry was performed on 1 wt % solutions ofo-Cl-HABI and CQ in tetrahydrofuran, and 1.1×10−4 M Tinuvin 328 and1×10−2 g/L Epolight 5675 in isopropyl alcohol using an AgilentTechnologies Cary 60 UV-Vis spectrophotometer. Spectra were collectedfrom 200 to 800 nm with 1 nm spacing on solutions using a 1 mm pathlength quartz cuvette in the dark.

For FT-IR spectroscopy, blue light was provided by a collimated,LED-based illumination source (Thorlabs M470L3-C1) with an emittancecentered at 470 nm (FWHM 25 nm), used in combination with acurrent-adjustable LED driver (Thorlabs LEDD1) for intensity control. UVlight was provided by a UV spot curing system (Omnicure LX500, ExcelitasTechnologies) equipped with an Omnicure LED MAX head with an emittancecentered at 365 nm. Irradiation intensities were measured with anInternational Light IL1400A radiometer equipped with a GaAsP Detector(model SEL005), a 10× attenuation neutral density filter (model QNDS1),and a quartz diffuser (model W).

Resin formulations were introduced between NaCl crystal windows(International Crystal Laboratories) separated by spacers (26 μm thickfor bisGMA/TEGDMA, 51 μm thick for BPAEDA, and 13 μm NPM/TEGDVE tomaintain constant sample thickness during polymerization. Each samplewas placed in a Thermo Scientific Nicolet 6700 FTIR spectrometerequipped with a horizontal transmission accessory, as describedpreviously, and spectra were collected from 650 to 4000 cm⁻¹ at a rateof 2 per second. The functional group conversion upon irradiation wasdetermined by monitoring the disappearance of the peak area centered at1635 cm⁻¹ for the methacrylate stretch, 1636 cm⁻¹ for the acrylatestretch, 1618 cm⁻¹ for the vinyl ether stretch, and 829 cm⁻¹ for themaleimide C═C double bond stretch. The respective sample thicknesses forthe formulations were chosen to ensure that the functional group peaksremained within the linear regime of the instrument detector whileaffording good signal to noise and maintaining optically thin andisothermal polymerization conditions. All experiments were performed intriplicate, and the photoinitiator and photoinhibitor concentrations andirradiation intensities were as indicated in the materials section andfigure captions.

For inhibition volume thickness measurements, UV light from a highpowered light emitting diode (LED) (λ_(max)=365 nm, 1400 mA, Thorlabs#M365LP1) was collimated using an aspheric condenser lens (ϕ=50 mm, F=32mm, NA=0.76, Thorlabs #ACL50832U) and focused with an adjustablecollimation adapter (Thorlabs #SM2F). Optical components were held inplace with a 60-mm cage cube system (Thorlabs #LC6 W). A high poweredblue LED (λ_(max)=458 nm, IF=1400 mA, Osram LE B Q7WP-5C8C-24) wasretrofitted into a commercial DLP projector (Optoma ML750). Light fromthe blue projection system passed through a bi-convex (ϕ=50 mm, F=100mm, NA=0.76, Thorlabs LB1630) lens to reduce the focal distance andsuperimposed with the UV light using a long pass dichroic mirror (ϕ=50mm, 425 nm cutoff, Thorlabs DMLP425L). The UV LED was driven by aBuckPuck LED driver (I=1000 mA, LEDdynamics Inc. 3023-D-E-1000) and theblue LED was driven by a constant current power supply (10000 mA, MeanWell HLG-120H-12B). The intensity of the LEDs were controlled using acustom LabVIEW virtual instrument (VI) which output a 0-5 V analogsignal which adjusted the current from the LED driver. Light intensityat a given voltage was calibrated by using an International LightIL1400A radiometer. 800 μm thick 3D-printed (Markforged Mark II, Nylon)spacers were affixed to a glass slide using epoxy adhesive to create awell for the photopolymer. Resin was pipetted into the well and sealedwith another glass slide. The resin was then cured for 10 s atI_(blue)=78.5 mW/cm² under with varying UV irradiation intensities togive 0<I_(UV)/I_(blue)<2. The cured resin was rinsed using isopropanoland re-exposed to blue light for an additional minute to completecuring. The thickness of the cured part was measured with a micrometer.The thickness of the inhibition volume was then calculated fromh_(IV)=h_(s)−h_(c) where h_(IV), h_(s), and h_(c) are the thicknesses ofthe inhibition volume, spacer, and cured plug, respectively.

For continuous 3D-printing, a custom build head was designed usingAutodesk Fusion 360 and fabricated out of nylon using 3D printing(Markforged Mark II). A metal base plate was attached at the base of thebuild head using two wingnuts. The build head was attached to acommercially available linear screw actuator (Rattmmotor CBX1605-300A)to enable vertical motion. Motion was controlled using an on/off digitalsignal from a custom Labview VI to start/stop a signal from a signalgenerator (Agilent 33220A). Models were designed using DesignsparkMechanical 2.0 or AutoDesk Fusion 360 and exported as STL files. Imageslices were created from STL files using Autodesk Netfabb 2017. Imageslices were displayed concurrently with the build head motion using aLabview VI. Parts were washed with isopropanol after printing to removeuncured resin.

Volumetric Polymerization Inhibition Patterning

The process (see, e.g., FIG. 8A) uses a build head that is drawn upwardsout of a photopolymerizable resin and two illumination sources atdifferent wavelengths. Patterned illumination from below through atransparent glass window initiates polymerization of the resin whileillumination at a second wavelength inhibits the polymerization reactionimmediately adjacent to the glass window, eliminating adhesion andenabling continuous operation. Print speeds of approximately 2 metersper hour have been achieved, and the process is compatible with a widevariety of resins including acrylates, methacrylates, and vinyl ethers.In addition, by varying the intensity of the light source on a per-pixelbasis, the system can perform true 3D printing in a singleexposure/layer with no stage translation.

In some embodiments, the system uses a multi-color system to achievevolumetric patterning by the photochemical generation of bothpolymerization initiation and polymerization inhibition species. Commonamongst all contemporary SLA devices is the use of a single wavelengthof light to initiate polymerization patterned in a plane. In contrast,the technology provided herein uses one wavelength to photochemicallyactivate polymerization and a second wavelength to inhibit thatreaction. Here, photopolymerizable resins are formulated withcamphorquinone (CQ, FIG. 8B) and ethyl-4-(dimethylamino) benzoate (EDAB,FIG. 8C), as a visible light photoinitiator and coinitiator,respectively, and bis[2-(o-chlorophenyl)-4,5-diphenylimidazole](o-Cl-HABI, FIG. 8D) as a photoinhibitor. Whereas HABIs are well knownas effective photoinitiators in the presence of complementary,hydrogen-donating co-initiators, in the absence of co-initiators, thelophyl radicals generated upon HABI photolysis efficiently inhibitradical-mediated, chain growth polymerization (FIG. 9) by rapidlyrecombining with propagating, carbon-centered radicals and thus can beused to prevent polymerization adjacent to the illumination window.

Data were collected measuring methacrylate conversion to polymer versustime for bisGMA/TEGDMA formulated with CQ/EDAB and o-Cl-HABI undercontinuous irradiation with 470 nm at 100 mW/cm² and intermittentirradiation with 365 nm at 30 mW/cm² for 30 seconds (FIG. 9, UVirradiation indicated by the shaded periods). The accumulation of lophylradicals during the 30 second UV irradiation periods afford decreasedpolymerization rates. Upon cessation of UV irradiation, thepolymerization rates recover after a lag time of approximately 30seconds during which the lophyl radicals recombine to relieve theinhibition.

Independently controlling initiation and inhibition necessitates thatphotoinitiating and photoinhibiting species have complementaryabsorbance spectra. As shown in FIG. 7, o-Cl-HABI exhibits very weakabsorbance in the blue region of the spectrum and moderate absorbance inthe near UV, complementing the absorbance spectrum of CQ which absorbsblue light (λ_(max)=470 nm) but absorbs poorly in the near UV. Thisminimal overlap in the absorbance spectra of CQ and o-Cl-HABI in thenear UV to blue region of the spectrum enables polymerization to beselectively initiated with blue light and inhibited with UV light.

The thickness of the polymerization inhibition volume can be controlledby varying the ratio of the intensities of the two illuminating lightsources. When both UV and blue light are supplied to the resin, aninhibition volume with no polymerization is generated adjacent to thewindow. Above this region, polymerization proceeds allowing thecontinuous printing of objects to proceed, such as those shown in FIG.8E, without deleterious window adhesion. Importantly, the inhibitionvolume thickness (e.g., the vertical distance into the resin from thetransparent window in which no polymerization occurs) is dependent onthe incident initiating and inhibiting light intensities, (I_(blue,0)and I_(UV,0), respectively) such that:

${Inhibition}\mspace{14mu}{volume}\mspace{14mu}{thickness}{= \frac{\log\left( \frac{\beta\; I_{{UV},0}}{I_{{blue},0}} \right)}{{1/h_{UV}} - {1/h_{blue}}}}$

Here, the inhibition coefficient (ß) is a constant for a given resincomposition, and incorporates the ratio of inhibitor to initiatorabsorbance cross sections, quantum yield, and reaction rate constants.The absorption height of a material, h_(UV) and h_(blue), is defined asthe inverse of the sum of the concentrations of all absorbing species(c_(i)) multiplied by their wavelength-specific absorptivity (ε_(i))

$h_{i} = \frac{1}{\sum{ɛ_{i}c_{i}}}$and is equal to the depth into an absorbing medium in which the light is90% attenuated.

FIG. 8F shows inhibition volume thickness, calculated using asubtractive technique, is controlled by varying both the ratios of theincident radiation and the concentration of the UV absorber. Adjustmentof I_(UV,0)/I_(blue,0) changes the relative rates of initiating andinhibiting radical generation within the resin (trimethylolpropanetriacrylate (TMPTA)) and can be used to control the inhibitionthickness. Alternatively, the UV absorber concentration (Tinuvin 328,see FIG. 14) can be changed to achieve a similar control over theinhibition volume thickness. Increasing the UV absorber concentration todecrease h_(UV) selectively confines UV light, and hence generation ofinhibiting radicals, to progressively thinner regions above theprojection window. It is important to note that a minimum intensityratio, at which initiation and inhibition rates are balanced, isrequired to generate an inhibition volume and can be shown to equal(I_(UV)/I_(blue))crit=1/ß. In this TMPTA-based system, 1/ß is found tobe approximately one; nevertheless, this value is dependent on resincomposition, necessitating experimental determination for specific resinformulations.

The thickness of this polymerization inhibition volume adjacent to theprojection window is a critical parameter for continuousstereolithographic fabrication. Previously reported inhibition layersresulting from oxygen inhibition are typically only tens of micrometersthick. Although this inhibition layer eliminates adhesion to the window,its small thickness curtails resin reflow underneath the emergentobject, especially in objects with large cross sectional areas, andnecessitates the use of low viscosity resins or fabrication of smallcross section objects. Here, the inhibition volume thickness can bemodulated by altering the UV absorbance of the resin or by varying theintensities of the initiating and inhibiting light sources, such thatinhibition volume thicknesses in the hundreds of microns are readilyobtained. These thick inhibition volumes are particularly desirable whenusing viscous resin formulations, further expanding the monomer palette,or to allow resin reflow into the print area for objects with largecross sectional areas. Nevertheless, increases in the inhibition volumethickness are typically accompanied by decreased polymerization rates,and hence slower print speeds, owing to attenuation of the initiationwavelength intensity within the resin bath. Notably, the systemdescribed here can negate this limitation and achieve equivalentpolymerization rates for different inhibition volume thicknesses byaccompanying any variation in the inhibition wavelength intensity with acorresponding initiation wavelength intensity change (see FIG. 13).

The large inhibition volume, in conjunction with high photoinitiationrates, facilitate continuous and rapid object printing. Notably, highphotoinitiation wavelength intensities to effect rapid polymerizationrates exacerbate separation and resin reflow issues in conventional anddiffusion-reliant methods, can be used in this system since theinhibiting intensity is adjustable to maintain an inhibition volume. Themaximum print speed for continuous printing in this system is a functionof the absorption heights at the inhibiting and initiating wavelengths,h_(UV) and h_(blue), the intensity of the initiating and inhibitingwavelength (I_(blue,0) here), and the amount of energy required to curethe resin, E_(c), such that:

${{{Max}.\mspace{11mu}{print}}\mspace{14mu}{speed}} \propto \frac{{I_{{blue},0}h_{blue}} - {\beta\; I_{{UV},0}h_{UV}}}{E_{c}}$

Practically, theoretical maximum print speed is difficult to achieveowing to lingering inhibiting radicals, mechanical properties of thecured resin, and reflow limitations dictated by the resin viscosity.Nevertheless, in some embodiments, the technology prints parts at speedsup to almost 2 meters per hour, e.g., for the gyroid structures shown inFIG. 12A. In this system, the depth to which light penetrates andultimately cures resin is controlled by modulating the resin's blueabsorbance (FIG. 12B) with the cured thickness for a given irradiationdose of initiating light given by:

${{Cured}\mspace{14mu}{Thickness}} = {h_{blue}{\log\left( \frac{I_{{blue},0}t}{E_{c}} \right)}}$where I_(blue,0)·t is the product of the irradiation intensity and time.Unwanted polymerization beyond the designed feature (known as “curethrough”) is present in resins with low absorbance causing poor verticalresolution. Adding blue-adsorbing dyes (e.g., Epolight 5675, see FIG.14) can remedy this but, as has been previously reported, a compromisebetween vertical resolution and print speed exists in continuous AMsystems (FIG. 12C).

The concurrent photoinitiation and photoinhibition described here can beapplied to a range of monomer classes for use in this AM system. HABIsexhibit several attributes favoring their potential as universalphotoinhibitors of radical-mediated, chain-growth polymerizations,including their favorable absorbance spectra and the inability ofHABI-derived lophyl radicals to directly initiate polymerization of(meth)acrylates, greatly expanding the compatible monomer palette. Todemonstrate the broad applicability of our photoinitiator/photoinhibitorsystem, acrylate, methacrylate, and vinyl ether/maleimide (e.g.,electron donor and electron acceptor monomers) resins (see FIG. 10A-E)formulated with CQ, EDAB, and o-Cl-HABI displayed rapid curing upon blueirradiation, suggesting that the HABI did not produce polymerizationrate-retarding chain transfer reactions, and while under exclusive nearUV irradiation, very limited to no curing was observed. Upon concurrentblue and near-UV irradiation, polymerization rates decreasedprecipitously relative to those observed under exclusively blueirradiation for all resin formulations examined, approaching zero forthe (meth)acrylates (FIG. 10F-H). Note that other two-color irradiationschemes have been demonstrated previously for sub-diffraction,direct-write photolithography. These systems used CQ and EDAB as a bluelight photoinitiator system and tetraethylthiuram disulfide (TETD) as aUV-active photoinhibitor. Unfortunately, the utility of TETD in rapidadditive manufacturing is hindered by its participation in chaintransfer reactions with propagating radical species, resulting insignificantly reduced photopolymerization rates at raised TETDconcentrations even under exclusively photoinitiating irradiation, whileco-irradiation at the photoinhibition wavelength yields reducedpolymerization rates but does not completely cease polymerization.Moreover, TETD has only been shown to effectively inhibit methacrylateresins, limiting the palette of compatible monomers.

In some embodiments, the technology comprises use of concurrentphotoinitiation and photoinhibition in conjunction with spatiallyspecific variation in light intensity to produce complex,three-dimensional surface features with a single, two-color exposure.Projecting blue images of variable intensities (e.g., varying theintensity on a pixel-by-pixel basis) against a constant UV backgroundaffords spatial variation of I_(UV,0)/I_(blue,0), consequently varyingthe inhibition volume thickness. This modulation creates a complex,three-dimensionally patterned inhibition volume, which enables localizedsurface patterning of features that is currently unattainable bycontemporary methods. FIG. 11A shows a schematic of this procedure wherethe single-exposure 3D printing was demonstrated with resin containingCQ/EDAB and o-Cl-HABI contained between two glass slides. The resin wasexposed to a blue image of varying intensity, and this image wassuperimposed on a uniform, collimated UV beam (FIG. 7A). A single tensecond exposure yields cured features with a thickness variation of upto 1200 μm (FIG. 11B). The magnitude of this variation can again bemodulated by adjusting the absorption characteristics of the resin viathe incorporation of dyes (e.g., by adjusting h_(UV) and h_(blue)). Theability to use this technique to produce patterned features withthree-dimensional structures is demonstrated with a four intensity-levelimage (FIG. 11). The cured resin resulting from exposure to the image inFIG. 11C shows the expected variation in thickness, and the 200 μm text5 features are readily resolved.

The controllable, concurrent photoinitiation and photoinhibition used inthis fabrication system has, in addition to high vertical print speeds,considerable advantages over contemporary approaches. By eliminating theneed for thin, O₂-permeable projection windows this process has thepotential to be scaled for rapid production of very large objects.Moreover, by dynamically controlling inhibition using this method,reflow into the inhibition volume during printing can be optimized toameliorate reflow problems associated with production of largecross-sectional area parts, significantly broadening the applicabilityof AM for mass production. Using variable intensity irradiation withconcurrent photoinitiation and photoinhibition allows single stepfabrication of cured materials with intricate surface topographies,enabling rapid generation of personalized products or to overcomenumerous time-consuming steps currently used in microfabrication. Theapplication of multi-wavelength systems to SLA is a new direction inadditive manufacturing where, in addition to the volumetricpolymerization control described here, two-color systems designed toeffect orthogonal reactions may enable fabrication of parts withlocalized material and chemical properties.

Bridged HABI Compounds with Fast Back-Reaction Kinetics

During the development of embodiments of the technology provided herein,experiments were conducted to test the polymerization initiation andinhibition in a composition and/or system comprising a bridged HABIcompound (see, e.g., FIG. 5A, 5B, 5C, 5D, and/or 5E). Adimethacrylate-based monomer mixture (50/50 bisGMA/TEGDMA; see FIG. 15)was formulated with 0.2% camphorquinone (CQ), 0.5%ethyl-4-(dimethylamino)benzoate (EDAB), 5% bridged HABI (e.g., acyclophane-based HABI (“pincer”)). CQ, EDAB, and bridged HABI weredissolved in THF prior to formulating with the monomer mixture.

Resin formulations were introduced between NaCl crystal windowsseparated by spacers (13 μm thick). Each sample was placed in a ThermoScientific Nicolet 6700 Fourier transform infrared (FTIR) spectrometerequipped with a horizontal transmission accessory, and spectra werecollected from 650 to 4000 cm⁻¹ at a rate of 2 per second as describedabove. The methacrylate conversion upon irradiation was determined bymonitoring the disappearance of the peak area centered at 1635 cm⁻¹.Data collected indicated the wavelength-selective photoinitiation andphotoinhibition of radical-mediated, chain growth photopolymerizationusing bridged HABI compound as a photoinhibitor (FIG. 16).

Blue light was provided by a collimated, light-emitting diode(LED)-based illumination source (Thorlabs M470L3-C1) with an emittancecentered at 470 nm, used in combination with a current-adjustable LEDdriver (Thorlabs LEDD1B) for intensity control. UV light was provided bya UV spot curing system (OmniCure LX500, Excelitas Technologies)equipped with an OmniCure LED MAX head with an emittance centered at 365nm.

Data collected indicated the wavelength-selective photoinitiation andphotoinhibition of radical-mediated, chain growth photopolymerizationusing bridged HABI compound as a photoinhibitor (FIG. 16).

Furthermore, data collected indicated the precise control ofpolymerization using the bridged HABI compound as a photoinhibitor.Methacrylate conversion to polymer versus time was measured forbisGMA/TEGDMA formulated with CQ/EDAB and a bridged HABI undercontinuous irradiation with 470 nm at 100 mW/cm² and intermittentirradiation with 365 nm at 30 mW/cm² for 30 second intervals (FIG. 17).In FIG. 17, irradiation by UV is indicated by the shaded time intervalsduring which polymerization rate slows. The accumulation of tetheredlophyl radicals during the 30 second UV irradiation periods decreasedand/or minimized polymerization rates. Upon cessation of UV irradiation(FIG. 17, non-shaded intervals), photoinhibition was also stopped andthe polymerization rate recovered instantaneously to the rate prior toUV irradiation owing to the fast recombination kinetics of the bridgedHABI compounds (FIG. 17, non-shaded period from approximately 45 secondsto 1 minute 45 seconds). By comparison, upon cessation of UV irradiationin similar experiments described above testing photoinhibition by anon-bridged HABI (e.g., o-Cl-HABI), polymerization resumed much moreslowly (with approximately a 30-second lag time) and did not resume apolymerization rate measured prior to UV irradiation (FIG. 9).

Accordingly, in some embodiments comprising use of a “precisephotoinhibitor” (e.g., a bridged HABI compound), the free-radicalchain-growth polymerization can be near-instantaneously “turned on” and“turned off” on the macro scale, a feat currently unattainable throughuse of the other photoinhibitors TETD and o-Cl-HABI.

Butyl Nitrite Photoinhibitors

During the development of embodiments of the technology describedherein, experiments were conducted to test photoinhibition by nitrites.Nitrites, both inorganic and organic, are known to be inhibitors orretarders of free-radical chain-growth polymerization. Inorganic nitritesalts can react with water to form nitric oxide and nitrous oxidespecies, while organic nitrites reportedly require activation to effectpolymerization inhibition. Thermal decomposition of organic nitritesresults in the formation of nitric oxide, an efficient inhibitor ofradical-mediated polymerizations, and alkoxide radicals which caninitiate polymerization. Higher molecular weight nitrites have beenexplored to inhibit styrene and butadiene polymerization duringdistillation, generally requiring low concentrations (0.0001-0.1%) to beeffective. Although alkyl nitrite photolysis has been extensivelyinvestigated, studies into their use as photoinhibitors has been limitedto an examination of butyl nitrite (BN) as a UV-activated inhibitor ofthermally-initiated, radical-mediated chain-growth polymerization. Assummarized in Scheme 1 (FIG. 18), this UV-induced photoinhibition wasattributed to the photolysis of BN, generating nitric oxide (1) which inturn affords a nitroso spin trap upon chain termination (2). This spintrap subsequently terminates a second propagating polymer chain (3), andthe generated nitroxide radical terminates another active radical center(4). Thus, although the alkoxy radical also generated by alkyl nitritephotolysis acts to initiate polymerization (5), one photolysis eventaffords a net two inhibition events.

Similar to TETD and o-Cl-HABI, BN exhibits very weak absorbance in theblue region of the spectrum and moderate absorbance in the near UV, thuscomplementing the absorbance spectrum of CQ, which has an absorbancemaximum near 470 nm while displaying very little ab-sorbance in the nearUV (FIG. 19). This enables for selective activation of either thephotoinitiator or the pho-toinhibitor through irradiation with blue ornear UV light, respectively.

Having established the optical compatibility between BN and CQ,experiments were conducted to explore the capacity of BN photolysis toinhibit free radical chain-growth photopolymerizations by formulatingBN, CQ, and EDAB (a coinitiator commonly used in conjunction with CQ) in(meth)acrylate resins. The conversion of (meth)acrylate functionalgroups was monitored by Fourier transform infrared (FTIR) spectroscopyduring the irradiation of formulated resins under irradiation with blue(470 nm) and near UV (365 nm) light. Negligible polymerization wasobserved for triethyleneglycol dimethacrylate (TEGDMA)/bisphenol Aglycidyl dimethacrylate (bisGMA) resin formulations containing BN uponirradiation at 365 nm (see FIG. 20A-D); indeed, an extended inductionperiod occurred even in the absence of BN (FIG. 20A), demonstrating thelow initiating radical generation rate afforded by the CQ/EDABphotoinitiator system under near UV irradiation. Whereas BN acts as aphotoinhibitor of the thermal bulk polymerization of methyl methacrylateunder near UV irradiation, it does not affect the polymerization withoutphotoactivation. In contrast, both the polymerization rate and overallconversion of the methacrylate formulations examined here under blueirradiation progressively decreased with raised BN concentration (seeFIG. 20A-D). Nevertheless, for resins formulated with low BNconcentrations, concurrent irradiation under both blue and near UV lightyielded significantly reduced polymerization rates relative to thoseattained under blue irradiation alone (FIGS. 20B and 20C), demonstratingthe ability of alkyl nitrites to act as photoinhibitors forradical-mediated methacrylate polymerizations.

To further evaluate the breadth of alkyl nitrite photoinhi-bitioncapacity, trimethylolpropane triacrylate (TMPTA)-based acrylate resinswere similarly formulated with BN, CQ, and EDAB, and theirphotopolymerization behaviour under blue and near UV irradiation wasexamined (see FIG. 21A-D). Under 365 nm irradiation, an extendedinduction period was again observed in the absence of BN; however,whereas no significant polymerization was observed for formulationscontaining low BN concentrations, some curing did proceed at a raised BNconcentration (see FIG. 21A-21D). Notably, under exclusively blue lightirradiation, only a modest decrease in polymerization rate was observedwith raised BN concentration. Irradiation with near-UV light led to.Photopolymerization inhibition under concurrent blue and near UVirradiation was significantly less effective for TMPTA than for thebis-GMA/TEGDMA system, potentially attributable to the higher reactivityof acrylates relative to methacrylate functional groups. Evaluation ofother (meth)acrylate monomers does indicate that the relativeeffectiveness of BN as a photoinhibitor seems to be verymonomer-dependent. Nevertheless, BN does allow for effectivephotoinhibition of various monomer formulations.

As described herein for the study of o-Cl-HABI as a photoinhibitor, onelimitation of o-Cl-HABI for some embodiments was the longer lifetime ofthe inhibiting lophyl radical. The impact of BN-derived radicals duringand post-activation was evaluated through monitoring the methacrylateconversion under constant blue irradiation, with periods of near-UVexposure. Through this, it was observed that BN photoinhibition waseffective and immediate upon near-UV exposure. Following near-UVirradiation, polymerization resumed rapidly, indicating promptconsumption of the inhibiting radicals in favor of polymer propagation.These results seem to contrast those of Sadykov, who reported asignificant induction time post-irradiation. This discrepancy could beexplained by the rates at which initiating radicals are being generated.While CQ initiated rapidly under our conditions, the conditions used bySadykov lead to a much slower generation of initiating radicals. Underthe conditions used in the experiments conducted during the developmentof embodiments of the technology described herein, the free-radicalchain-growth polymerization can be near-instantaneously “turned on” and“turned off” on the macro scale, a feat currently unattainable throughuse of the other photoinhibitors TETD and o-Cl-HABI.

Having determined BN as an effective photoinhibitor of TMPTA, withsignificant differences between exclusive blue curing and concurrentcuring, experiments were conducted to test the difference in curingtimes through a photomask litho-graphic approach. The resin on atransparent surface was irradiated uniformly through the surface withthe initiating wavelength, while being irradiated through a photomaskwith the inhibiting wavelength. As a result of this, the region blockedfrom near-UV irradiation cures rapidly, while the exposed areas remainliquid and can be washed away with solvent. Through this approachembodiments of the technology inhibit polymerization to up to 5 mm ofresin, while still achieving effective polymerization of simple shapes.

While the patterning though photomask inhibition in 2D serves itspurpose as a demonstration of the concept, the use of this approach islimited, as the same result can be obtained through irradiation of theresin with curing light through a negative photomask. This patterning ofphotoinitiating and photoinhibiting lights does open up opportunitiesfor the manufacturing of more complex 3D structures. For example, asdescribed herein, perpendicular irradiation of initiating and inhibitinglights provide for the production of more complex 3D structures in asingle exposure of the two colors of light. In this example of a quartzcuvette, blue light is patterned through a triangular photomask,resulting in the curing of the resin into a triangular prism.Perpendicular to the blue irradiation, near-UV light is irradiatedthrough a circular photomask. As a result, the pattern of near-UV lightis prevented from being cured by the blue light, producing a triangularprism with a circle shape inhibited through the center in a singleexposure of the two colors of light. Manufacturing a similar piece witha single light exposure is not attainable through contemporaryapproaches, and this technique opens up a new direction of “true” 3Dprinting.

In conclusion, embodiments provide use of butyl nitrite as aphotoinhibitor of free-radical chain-growth photopolymerizations, e.g.,in a two-color irradiation setup. In some embodiments, the effectivenessof BN as a photoinhibitor is strongly monomer dependent, and inclusionof BN can lead to reduced polymerization without BN activation. Incontrast to previously-reported work, the inhibiting radicals appear tocease inhibition shortly following the removal of near-UV irradiation.BN proved effective for 2D patterning of the inhibition through aphotomask, the results of which translated effectively to a 3Dirradiation setup. This allows for rapid, single-exposure fabrication ofmore complex structures otherwise unattainable, and opening up the pathfor a new approach to “true” 3D printing.

Two-Wavelength Dead Zone Control

During the development of embodiments of the technology provided herein,a continuous liquid interphase production system was designed. Duringthe development of embodiments of the technology, experiments weredesigned to test and implement resins into a continuous 3D printingsystem. In some embodiments, the technology finds use to improve thespeed of printing parts having small cross sectional areas.

The standard resin system used in these experiments comprises componentspreviously described (Scott et al. (2009) “Two-Color Single-PhotoPhotoinitiation and Photoinhibition for Subdiffraction Photolithography”Science 324: 913-17). This system comprises a composition comprisingcamphorquinone (CQ), ethyl-dimethylamino benzoate (EDAB),tetraethylthiuram disulfide (TED), and triethylene glycol dimethacrylate(TEGDMA). CQ and EDAB are the initiators and co-initiator, respectively.This initiator system is activated by blue light and has very littleabsorbance in the UV range. TED is the UV-activated photoinhibitor andTEGDMA is the methacrylate polymerizable monomer. During the developmentof embodiments of the technology, a composition comprises 1.0/0.5/3.0 wt% CQ/EDAB/TED in TEGDMA (see Scott et al., supra).

Experiments use an optical system that simultaneously irradiates theresin with blue light and UV light. A simplified schematic of this setupis shown in FIG. 26. In the exemplary embodiment shown in FIG. 26, thesystem comprises two light sources—a UV source (e.g., a VISITECH LE4960HUV-388) and a blue light source (e.g. DLP LIGHTCRAFTER 4500 fitted witha blue LED source at 473 nm). The system further comprises a long passdichroic mirror with a 425 nm cutoff (e.g. the THORLA3S DMLP425L). TheDLP provides patterns of irradiating light, which projects patterns asdirected by a software object (e.g., encoded in a stereolithography file(“STL” file or “PLY” file or other file type) as known in the art for 3Dprinting).

During the development of embodiments of the technology, the molarabsorption coefficients of resins at the wavelengths of interest arecalculated using a spectrophotometer and standard methods.Beer-Lambert's law is used to model the intensity levels within theresin bath to determine rough estimates for experimental conditions totest. In some embodiments, the technology provides at least anorder-of-magnitude improvement in dead zone thickness relative tooxygen-inhibited CLIP, which is approximately 100 μm to 1000 μm.Accordingly, the technology provided herein produces a dead zone havinga thickness of at least approximately 1 mm to 10 mm (e.g., at leastapproximately 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mm). In some embodiments,the technology provided herein produces a dead zone having a thicknessthat is greater than 10 mm.

During the development of embodiments of the technology describedherein, the dead zone thickness is measured according to Tumbleston etal. (Tumbleston et al. (2015). “Continuous liquid interface productionof 3D objects, Science 347: 1349-52) with some modification. Inparticular, experiments are conducted in which a known thickness ofliquid resin (Z_(R)) is placed between a glass slide and the projectionwindow. The UV intensity and exposure time are varied over a range ofblue light intensity levels. After irradiation, the thickness of thecured resin (Z_(C)) is measured using a standard thickness probe, suchthat the thickness of the dead zone is calculated by subtraction(Z_(D)=Z_(R)−Z_(C)).

In some embodiments, compositions comprise a photoinitiator having amolar absorption coefficient for the activating wavelength (e.g., UV forTED) that is not sufficient to form a dead zone of millimeter thickness.Accordingly, in some embodiments, the compositions further comprise a UVabsorber to increase the absorbance of UV wavelengths and reduce thedead zone thickness. Thus, experiments are performed during thedevelopment of some embodiments of the technology using the abovementioned method to investigate the effect of UV absorber concentrationon the thickness of the dead zone.

In some alternative embodiments, the technology comprises lateralprojection of the inhibiting wavelength (e.g., high intensity light(e.g., UV light)) to inhibit an entire cross section of the resin bathas described herein and in U.S. Prov. Pat. App. Ser. No. 62/632,903,which is expressly incorporated herein by reference in its entirety.

In some embodiments, light is provided as an evanescent waves (e.g.,high intensity light (e.g., UV light)) to inhibit polymerization in athin region at the window. See, e.g., Fuchs et al. (2011). “UltrathinSelective Molecularly Imprinted Polymer Microdots Obtained by EvanescentWave Photopolymerization” Chemistry of Materials 23: 3645-51.Accordingly, embodiments comprising use of light provided as anevanescent wave provide a technology for producing inhibition (e.g., toproduce a dead zone) that is controllable independently from theinitiating light.

Some embodiments comprise use of oxygen inhibition to produce acontrollable dead zone, however embodiments comprise use of a UV-activewater cleaving catalyst such as CoO rather than supplying O₂ through bydiffusion (see, e.g., Liao et al. (2014). “Efficient solarwater-splitting using a nanocrystalline CoO photocatalyst” NatureNanotechnology 9: 69-73). In some embodiments, this technology providesbetter control over the dead zone than extant O₂-based strategies fordead zone inhibition, and hence provides a technology comprising use ofhigher initiating intensities and thus improved print speeds relative toextant technologies.

During the development of embodiments of the technology describedherein, experiments are conducted to incorporate a standard resin into acontinuous 3D printing system as described herein. In particular,embodiments comprise use of the optical setup described above (FIG. 26)that is further modified to include a controllable build plate similarto those in most stereolithographic 3D printer systems. Accordingly,embodiments comprise a system for 3D printing comprising a build platethat is capable of being raised and lowered at very precise rates. Insome embodiments, this assembly is repurposed from an extant 3D printer.In some embodiments, the assembly is a custom system comprising a linearbeam actuator fitted with a controllable stepper motor and an Arduinocontrol module capable of precisely controlling the stepping.

During the development of some embodiments of the technology,experiments are conducted in which the thickness of the cured resin atthe provided dead zone thickness is measured as a function of time. Inparticular, measurement of the polymerization rates at differentintensity ratios is measured using standard techniques to estimate thecuring rate of the polymer at the dead zone interface. For instance,some experiments test curing rate by projecting simple patterns of theinitiating wavelength (e.g., using the DLP LIGHTCRAFTER 4500) andraising the build plate at various speeds to determine the finalachievable print speed.

In some extant technologies, photo-polymerizing a monomer at acontrolled depth is sometimes compromised by “through-polymerization”,which is when a curing light passes through the desired depth and curesresin beyond the desired depth. In 3D printing this causes poorresolution of features in the vertical dimension. Accordingly, in someembodiments, the penetration of curing light is controlled by adjustingthe absorbance of curing light in the resin. In particular, experimentsconducted during the development of the technology provided hereinadjust the concentration of CQ in the resin or incorporate blue lightabsorbers (such as those available from Everlight Chemical) to controlthe depth of penetration of the initiating wavelength of light.

During the development of embodiments of the technology provided herein,experiments are conduced to test various resins (e.g., polymerizablemonomers) and/or photoinitiators and/or photoinhibitors. Embodiments ofthe technology provide for the production of parts comprising materialshaving a wide range of physical properties. While embodiments comprisinguse of the standard resin described above are tested to using aUV-controllable dead zone, experiments are conducted also to test othermaterials that provide properties such as flexibility, opticaltransparency, and mechanical strength. Thus, embodiments relate toapplying the technologies provided to a wide variety of resincompositions, e.g., different monomers, to produce items havingproperties such as a wide range of hardness or optical characteristics.

All publications and patents mentioned in the above specification areherein incorporated by reference in their entirety for all purposes.Various modifications and variations of the described compositions,methods, and uses of the technology will be apparent to those skilled inthe art without departing from the scope and spirit of the technology asdescribed. Although the technology has been described in connection withspecific exemplary embodiments, it should be understood that theinvention as claimed should not be unduly limited to such specificembodiments. Indeed, various modifications of the described modes forcarrying out the invention that are obvious to those skilled in the artare intended to be within the scope of the following claims.

We claim:
 1. A method of producing a polymerized item, the methodcomprising: a) providing a composition comprising a polymerizablemonomer and a photoinitiator; and b) irradiating said composition withan intensity-patterned image comprising a plurality of pixels, whereinsaid plurality of pixels comprises pixels providing a first wavelengthof light at more than two intensities, wherein irradiating saidcomposition with said first wavelength of light produces an initiatingspecies from the photoinitiator and wherein said initiating speciespolymerizes polymerizable monomers to produce at least a portion of apolymerized item.
 2. The method of claim 1, wherein said plurality ofpixels comprises pixels providing a first wavelength of light at four ormore intensities.
 3. The method of claim 1, wherein saidintensity-patterned image comprising a plurality of pixels is agrayscale-patterned image.
 4. The method of claim 1, wherein saidintensity-patterned image comprising a plurality of pixels provides athree-dimensional contour of light intensity of the first wavelength oflight.
 5. The method of claim 1, further comprising varying an intensityof a pixel of said intensity-patterned image.
 6. The method of claim 1,further comprising changing the intensity-patterned image.
 7. The methodof claim 1, wherein said intensity-patterned image comprises a millionpixels.
 8. The method of claim 1, wherein said polymerized item variesin thickness in a dimension substantially parallel to the direction ofsaid first wavelength of light.
 9. The method of claim 8, wherein saiditem comprises cured features with a thickness variation of up to 1200μm.
 10. The method of claim 1, wherein said composition furthercomprises a photoinhibitor and the method further comprises irradiatingsaid composition with a second wavelength of light to produce a deadzone comprising an inhibiting species produced from the photoinhibitorand said initiating species is produced above the dead zone.
 11. Themethod of claim 10, wherein said photoinhibitor comprises ahexaarylbiimidazole (HABI).
 12. A method of producing a polymerizeditem, the method comprising a) providing a composition comprising apolymerizable monomer, a photoinitiator, and a photoinhibitor; b)irradiating said composition with a first wavelength of light to producea dead zone comprising an inhibiting species produced from thephotoinhibitor; and c) irradiating said composition with a secondwavelength of light to produce an initiating species from thephotoinitiator above the dead zone, wherein said initiating speciespolymerizes polymerizable monomers to produce at least a portion of apolymerized item, wherein one or both of: i) irradiating saidcomposition with a first wavelength of light comprises irradiating saidcomposition with a first light intensity-patterned image comprising afirst plurality of pixels, wherein said first plurality of pixelscomprises pixels providing said first wavelength of light at more thantwo intensities; and/or ii) irradiating said composition with a secondwavelength of light comprises irradiating said composition with a secondlight intensity-patterned image comprising a second plurality of pixels,wherein said second plurality of pixels comprises pixels providing saidsecond wavelength of light at more than two intensities.
 13. The methodof claim 12, wherein said first wavelength of light is ultraviolet lighthaving a wavelength of approximately 100-450 nm and/or said secondwavelength of light is blue light having a wavelength of approximately450-495 nm.
 14. The method of claim 12, wherein said first lightintensity-patterned image comprises pixels providing said firstwavelength of light at four or more intensities and/or said second lightintensity-patterned image comprises pixels providing said secondwavelength of light at four or more intensities.
 15. The method of claim12, wherein said first light intensity-patterned image is agrayscale-patterned image and/or said second light intensity-patternedimage is a grayscale-patterned image.
 16. The method of claim 12,wherein said first light intensity-patterned image provides athree-dimensional contour of light intensity and/or said second lightintensity-patterned image provides a three-dimensional contour of lightintensity.
 17. The method of claim 12, further comprising varying anintensity of a pixel of said first intensity-patterned image and/orvarying an intensity of a pixel of said second intensity-patternedimage.
 18. The method of claim 12, further comprising changing saidfirst light intensity-patterned image and/or changing said second lightintensity-patterned image.
 19. The method of claim 12, wherein saidfirst light intensity-patterned image comprises a million pixels and/orsaid second light intensity-patterned image comprises a million pixels.20. The method of claim 12, further comprising: d) changing said firstlight intensity-patterned image to provide a first changedintensity-patterned image and/or changing said second lightintensity-patterned image to provide a second changedintensity-patterned image; and e) irradiating said composition with saidfirst and/or second changed intensity-patterned image to produce asecond portion of said polymerized item.